author | Lennard de Rijk <ljvderijk@gmail.com> |
Tue, 07 Apr 2009 22:22:43 +0000 | |
changeset 2126 | df06ceda7dcc |
parent 109 | 620f9b141567 |
permissions | -rw-r--r-- |
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The Django template language: For Python programmers |
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==================================================== |
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This document explains the Django template system from a technical |
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perspective -- how it works and how to extend it. If you're just looking for |
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reference on the language syntax, see |
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`The Django template language: For template authors`_. |
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If you're looking to use the Django template system as part of another |
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application -- i.e., without the rest of the framework -- make sure to read |
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the `configuration`_ section later in this document. |
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.. _`The Django template language: For template authors`: ../templates/ |
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Basics |
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====== |
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A **template** is a text document, or a normal Python string, that is marked-up |
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using the Django template language. A template can contain **block tags** or |
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**variables**. |
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A **block tag** is a symbol within a template that does something. |
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This definition is deliberately vague. For example, a block tag can output |
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content, serve as a control structure (an "if" statement or "for" loop), grab |
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content from a database or enable access to other template tags. |
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Block tags are surrounded by ``"{%"`` and ``"%}"``. |
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Example template with block tags:: |
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{% if is_logged_in %}Thanks for logging in!{% else %}Please log in.{% endif %} |
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A **variable** is a symbol within a template that outputs a value. |
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Variable tags are surrounded by ``"{{"`` and ``"}}"``. |
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Example template with variables:: |
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My first name is {{ first_name }}. My last name is {{ last_name }}. |
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A **context** is a "variable name" -> "variable value" mapping that is passed |
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to a template. |
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A template **renders** a context by replacing the variable "holes" with values |
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from the context and executing all block tags. |
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Using the template system |
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========================= |
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Using the template system in Python is a two-step process: |
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* First, you compile the raw template code into a ``Template`` object. |
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* Then, you call the ``render()`` method of the ``Template`` object with a |
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given context. |
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Compiling a string |
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------------------ |
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The easiest way to create a ``Template`` object is by instantiating it |
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directly. The class lives at ``django.template.Template``. The constructor |
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takes one argument -- the raw template code:: |
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>>> from django.template import Template |
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>>> t = Template("My name is {{ my_name }}.") |
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>>> print t |
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<django.template.Template instance> |
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.. admonition:: Behind the scenes |
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The system only parses your raw template code once -- when you create the |
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``Template`` object. From then on, it's stored internally as a "node" |
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structure for performance. |
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Even the parsing itself is quite fast. Most of the parsing happens via a |
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single call to a single, short, regular expression. |
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Rendering a context |
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------------------- |
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Once you have a compiled ``Template`` object, you can render a context -- or |
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multiple contexts -- with it. The ``Context`` class lives at |
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``django.template.Context``, and the constructor takes one (optional) |
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argument: a dictionary mapping variable names to variable values. Call the |
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``Template`` object's ``render()`` method with the context to "fill" the |
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template:: |
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>>> from django.template import Context, Template |
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>>> t = Template("My name is {{ my_name }}.") |
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>>> c = Context({"my_name": "Adrian"}) |
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>>> t.render(c) |
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"My name is Adrian." |
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>>> c = Context({"my_name": "Dolores"}) |
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>>> t.render(c) |
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"My name is Dolores." |
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Variable names must consist of any letter (A-Z), any digit (0-9), an underscore |
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or a dot. |
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Dots have a special meaning in template rendering. A dot in a variable name |
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signifies **lookup**. Specifically, when the template system encounters a dot |
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in a variable name, it tries the following lookups, in this order: |
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* Dictionary lookup. Example: ``foo["bar"]`` |
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* Attribute lookup. Example: ``foo.bar`` |
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* Method call. Example: ``foo.bar()`` |
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* List-index lookup. Example: ``foo[bar]`` |
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The template system uses the first lookup type that works. It's short-circuit |
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logic. |
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114 |
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115 |
Here are a few examples:: |
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116 |
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117 |
>>> from django.template import Context, Template |
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118 |
>>> t = Template("My name is {{ person.first_name }}.") |
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119 |
>>> d = {"person": {"first_name": "Joe", "last_name": "Johnson"}} |
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120 |
>>> t.render(Context(d)) |
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121 |
"My name is Joe." |
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122 |
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123 |
>>> class PersonClass: pass |
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>>> p = PersonClass() |
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>>> p.first_name = "Ron" |
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126 |
>>> p.last_name = "Nasty" |
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127 |
>>> t.render(Context({"person": p})) |
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128 |
"My name is Ron." |
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129 |
|
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130 |
>>> class PersonClass2: |
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131 |
... def first_name(self): |
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... return "Samantha" |
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>>> p = PersonClass2() |
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134 |
>>> t.render(Context({"person": p})) |
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135 |
"My name is Samantha." |
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136 |
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137 |
>>> t = Template("The first stooge in the list is {{ stooges.0 }}.") |
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>>> c = Context({"stooges": ["Larry", "Curly", "Moe"]}) |
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139 |
>>> t.render(c) |
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140 |
"The first stooge in the list is Larry." |
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141 |
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142 |
Method lookups are slightly more complex than the other lookup types. Here are |
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143 |
some things to keep in mind: |
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144 |
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145 |
* If, during the method lookup, a method raises an exception, the exception |
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146 |
will be propagated, unless the exception has an attribute |
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147 |
``silent_variable_failure`` whose value is ``True``. If the exception |
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148 |
*does* have a ``silent_variable_failure`` attribute, the variable will |
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149 |
render as an empty string. Example:: |
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150 |
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151 |
>>> t = Template("My name is {{ person.first_name }}.") |
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152 |
>>> class PersonClass3: |
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153 |
... def first_name(self): |
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154 |
... raise AssertionError, "foo" |
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155 |
>>> p = PersonClass3() |
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156 |
>>> t.render(Context({"person": p})) |
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157 |
Traceback (most recent call last): |
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158 |
... |
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159 |
AssertionError: foo |
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160 |
|
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161 |
>>> class SilentAssertionError(Exception): |
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162 |
... silent_variable_failure = True |
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163 |
>>> class PersonClass4: |
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164 |
... def first_name(self): |
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165 |
... raise SilentAssertionError |
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166 |
>>> p = PersonClass4() |
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167 |
>>> t.render(Context({"person": p})) |
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168 |
"My name is ." |
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169 |
|
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170 |
Note that ``django.core.exceptions.ObjectDoesNotExist``, which is the |
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171 |
base class for all Django database API ``DoesNotExist`` exceptions, has |
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172 |
``silent_variable_failure = True``. So if you're using Django templates |
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173 |
with Django model objects, any ``DoesNotExist`` exception will fail |
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174 |
silently. |
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175 |
|
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176 |
* A method call will only work if the method has no required arguments. |
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177 |
Otherwise, the system will move to the next lookup type (list-index |
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178 |
lookup). |
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179 |
|
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180 |
* Obviously, some methods have side effects, and it'd be either foolish or |
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181 |
a security hole to allow the template system to access them. |
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182 |
|
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183 |
A good example is the ``delete()`` method on each Django model object. |
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184 |
The template system shouldn't be allowed to do something like this:: |
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185 |
|
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186 |
I will now delete this valuable data. {{ data.delete }} |
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187 |
|
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188 |
To prevent this, set a function attribute ``alters_data`` on the method. |
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189 |
The template system won't execute a method if the method has |
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190 |
``alters_data=True`` set. The dynamically-generated ``delete()`` and |
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191 |
``save()`` methods on Django model objects get ``alters_data=True`` |
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192 |
automatically. Example:: |
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193 |
|
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194 |
def sensitive_function(self): |
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195 |
self.database_record.delete() |
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196 |
sensitive_function.alters_data = True |
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197 |
|
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198 |
How invalid variables are handled |
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199 |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
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200 |
|
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201 |
Generally, if a variable doesn't exist, the template system inserts the |
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202 |
value of the ``TEMPLATE_STRING_IF_INVALID`` setting, which is set to ``''`` |
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203 |
(the empty string) by default. |
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204 |
|
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205 |
Filters that are applied to an invalid variable will only be applied if |
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206 |
``TEMPLATE_STRING_IF_INVALID`` is set to ``''`` (the empty string). If |
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207 |
``TEMPLATE_STRING_IF_INVALID`` is set to any other value, variable |
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208 |
filters will be ignored. |
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209 |
|
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210 |
This behavior is slightly different for the ``if``, ``for`` and ``regroup`` |
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211 |
template tags. If an invalid variable is provided to one of these template |
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212 |
tags, the variable will be interpreted as ``None``. Filters are always |
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213 |
applied to invalid variables within these template tags. |
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214 |
|
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215 |
.. admonition:: For debug purposes only! |
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216 |
|
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217 |
While ``TEMPLATE_STRING_IF_INVALID`` can be a useful debugging tool, |
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218 |
it is a bad idea to turn it on as a 'development default'. |
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219 |
|
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220 |
Many templates, including those in the Admin site, rely upon the |
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221 |
silence of the template system when a non-existent variable is |
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222 |
encountered. If you assign a value other than ``''`` to |
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223 |
``TEMPLATE_STRING_IF_INVALID``, you will experience rendering |
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224 |
problems with these templates and sites. |
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225 |
|
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Generally, ``TEMPLATE_STRING_IF_INVALID`` should only be enabled |
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in order to debug a specific template problem, then cleared |
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once debugging is complete. |
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229 |
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Playing with Context objects |
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---------------------------- |
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232 |
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Most of the time, you'll instantiate ``Context`` objects by passing in a |
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fully-populated dictionary to ``Context()``. But you can add and delete items |
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from a ``Context`` object once it's been instantiated, too, using standard |
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dictionary syntax:: |
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237 |
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>>> c = Context({"foo": "bar"}) |
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>>> c['foo'] |
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'bar' |
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>>> del c['foo'] |
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>>> c['foo'] |
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'' |
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>>> c['newvariable'] = 'hello' |
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>>> c['newvariable'] |
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'hello' |
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247 |
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A ``Context`` object is a stack. That is, you can ``push()`` and ``pop()`` it. |
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If you ``pop()`` too much, it'll raise |
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``django.template.ContextPopException``:: |
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251 |
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>>> c = Context() |
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>>> c['foo'] = 'first level' |
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>>> c.push() |
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>>> c['foo'] = 'second level' |
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>>> c['foo'] |
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'second level' |
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>>> c.pop() |
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259 |
>>> c['foo'] |
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'first level' |
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>>> c['foo'] = 'overwritten' |
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>>> c['foo'] |
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'overwritten' |
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>>> c.pop() |
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Traceback (most recent call last): |
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... |
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267 |
django.template.ContextPopException |
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268 |
|
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Using a ``Context`` as a stack comes in handy in some custom template tags, as |
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you'll see below. |
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271 |
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Subclassing Context: RequestContext |
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----------------------------------- |
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274 |
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Django comes with a special ``Context`` class, |
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``django.template.RequestContext``, that acts slightly differently than |
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the normal ``django.template.Context``. The first difference is that takes |
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an `HttpRequest object`_ as its first argument. For example:: |
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279 |
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c = RequestContext(request, { |
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'foo': 'bar', |
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} |
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283 |
|
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The second difference is that it automatically populates the context with a few |
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variables, according to your `TEMPLATE_CONTEXT_PROCESSORS setting`_. |
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286 |
|
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The ``TEMPLATE_CONTEXT_PROCESSORS`` setting is a tuple of callables -- called |
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**context processors** -- that take a request object as their argument and |
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return a dictionary of items to be merged into the context. By default, |
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``TEMPLATE_CONTEXT_PROCESSORS`` is set to:: |
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291 |
|
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292 |
("django.core.context_processors.auth", |
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293 |
"django.core.context_processors.debug", |
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294 |
"django.core.context_processors.i18n") |
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295 |
|
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296 |
Each processor is applied in order. That means, if one processor adds a |
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297 |
variable to the context and a second processor adds a variable with the same |
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298 |
name, the second will override the first. The default processors are explained |
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299 |
below. |
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300 |
|
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301 |
Also, you can give ``RequestContext`` a list of additional processors, using the |
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optional, third positional argument, ``processors``. In this example, the |
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``RequestContext`` instance gets a ``ip_address`` variable:: |
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304 |
|
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305 |
def ip_address_processor(request): |
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306 |
return {'ip_address': request.META['REMOTE_ADDR']} |
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307 |
|
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308 |
def some_view(request): |
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309 |
# ... |
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310 |
return RequestContext(request, { |
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311 |
'foo': 'bar', |
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312 |
}, [ip_address_processor]) |
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313 |
|
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314 |
Note:: |
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315 |
If you're using Django's ``render_to_response()`` shortcut to populate a |
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316 |
template with the contents of a dictionary, your template will be passed a |
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``Context`` instance by default (not a ``RequestContext``). To use a |
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``RequestContext`` in your template rendering, pass an optional third |
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argument to ``render_to_response()``: a ``RequestContext`` |
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320 |
instance. Your code might look like this:: |
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321 |
|
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322 |
def some_view(request): |
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323 |
# ... |
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324 |
return render_to_response('my_template.html', |
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325 |
my_data_dictionary, |
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326 |
context_instance=RequestContext(request)) |
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327 |
|
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328 |
Here's what each of the default processors does: |
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329 |
|
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330 |
.. _HttpRequest object: ../request_response/#httprequest-objects |
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331 |
.. _TEMPLATE_CONTEXT_PROCESSORS setting: ../settings/#template-context-processors |
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332 |
|
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333 |
django.core.context_processors.auth |
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334 |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
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335 |
|
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336 |
If ``TEMPLATE_CONTEXT_PROCESSORS`` contains this processor, every |
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337 |
``RequestContext`` will contain these three variables: |
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338 |
|
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339 |
* ``user`` -- An ``auth.User`` instance representing the currently |
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340 |
logged-in user (or an ``AnonymousUser`` instance, if the client isn't |
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341 |
logged in). See the `user authentication docs`. |
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342 |
|
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343 |
* ``messages`` -- A list of messages (as strings) for the currently |
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344 |
logged-in user. Behind the scenes, this calls |
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345 |
``request.user.get_and_delete_messages()`` for every request. That method |
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346 |
collects the user's messages and deletes them from the database. |
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347 |
|
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348 |
Note that messages are set with ``user.add_message()``. See the |
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349 |
`message docs`_ for more. |
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350 |
|
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351 |
* ``perms`` -- An instance of |
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352 |
``django.core.context_processors.PermWrapper``, representing the |
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353 |
permissions that the currently logged-in user has. See the `permissions |
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354 |
docs`_. |
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355 |
|
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356 |
.. _user authentication docs: ../authentication/#users |
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357 |
.. _message docs: ../authentication/#messages |
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358 |
.. _permissions docs: ../authentication/#permissions |
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359 |
|
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360 |
django.core.context_processors.debug |
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361 |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
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362 |
|
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363 |
If ``TEMPLATE_CONTEXT_PROCESSORS`` contains this processor, every |
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364 |
``RequestContext`` will contain these two variables -- but only if your |
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365 |
``DEBUG`` setting is set to ``True`` and the request's IP address |
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366 |
(``request.META['REMOTE_ADDR']``) is in the ``INTERNAL_IPS`` setting: |
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367 |
|
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368 |
* ``debug`` -- ``True``. You can use this in templates to test whether |
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369 |
you're in ``DEBUG`` mode. |
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370 |
* ``sql_queries`` -- A list of ``{'sql': ..., 'time': ...}`` dictionaries, |
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371 |
representing every SQL query that has happened so far during the request |
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372 |
and how long it took. The list is in order by query. |
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373 |
|
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374 |
django.core.context_processors.i18n |
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375 |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
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|
376 |
|
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377 |
If ``TEMPLATE_CONTEXT_PROCESSORS`` contains this processor, every |
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|
378 |
``RequestContext`` will contain these two variables: |
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|
379 |
|
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380 |
* ``LANGUAGES`` -- The value of the `LANGUAGES setting`_. |
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381 |
* ``LANGUAGE_CODE`` -- ``request.LANGUAGE_CODE``, if it exists. Otherwise, |
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382 |
the value of the `LANGUAGE_CODE setting`_. |
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|
383 |
|
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384 |
See the `internationalization docs`_ for more. |
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|
385 |
|
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|
386 |
.. _LANGUAGES setting: ../settings/#languages |
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|
387 |
.. _LANGUAGE_CODE setting: ../settings/#language-code |
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|
388 |
.. _internationalization docs: ../i18n/ |
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|
389 |
|
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|
390 |
django.core.context_processors.request |
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|
391 |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
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|
392 |
|
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|
393 |
If ``TEMPLATE_CONTEXT_PROCESSORS`` contains this processor, every |
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|
394 |
``RequestContext`` will contain a variable ``request``, which is the current |
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|
395 |
`HttpRequest object`_. Note that this processor is not enabled by default; |
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|
396 |
you'll have to activate it. |
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|
397 |
|
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|
398 |
Writing your own context processors |
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|
399 |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
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|
400 |
|
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|
401 |
A context processor has a very simple interface: It's just a Python function |
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|
402 |
that takes one argument, an ``HttpRequest`` object, and returns a dictionary |
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|
403 |
that gets added to the template context. Each context processor *must* return |
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|
404 |
a dictionary. |
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|
405 |
|
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|
406 |
Custom context processors can live anywhere in your code base. All Django cares |
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|
407 |
about is that your custom context processors are pointed-to by your |
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|
408 |
``TEMPLATE_CONTEXT_PROCESSORS`` setting. |
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|
409 |
|
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|
410 |
Loading templates |
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|
411 |
----------------- |
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|
412 |
|
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|
413 |
Generally, you'll store templates in files on your filesystem rather than using |
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|
414 |
the low-level ``Template`` API yourself. Save templates in a directory |
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|
415 |
specified as a **template directory**. |
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|
416 |
|
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|
417 |
Django searches for template directories in a number of places, depending on |
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|
418 |
your template-loader settings (see "Loader types" below), but the most basic |
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|
419 |
way of specifying template directories is by using the ``TEMPLATE_DIRS`` |
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|
420 |
setting. |
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|
421 |
|
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|
422 |
The TEMPLATE_DIRS setting |
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|
423 |
~~~~~~~~~~~~~~~~~~~~~~~~~ |
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|
424 |
|
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|
425 |
Tell Django what your template directories are by using the ``TEMPLATE_DIRS`` |
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|
426 |
setting in your settings file. This should be set to a list or tuple of strings |
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|
427 |
that contain full paths to your template directory(ies). Example:: |
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|
428 |
|
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|
429 |
TEMPLATE_DIRS = ( |
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|
430 |
"/home/html/templates/lawrence.com", |
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|
431 |
"/home/html/templates/default", |
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|
432 |
) |
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|
433 |
|
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|
434 |
Your templates can go anywhere you want, as long as the directories and |
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|
435 |
templates are readable by the Web server. They can have any extension you want, |
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|
436 |
such as ``.html`` or ``.txt``, or they can have no extension at all. |
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|
437 |
|
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|
438 |
Note that these paths should use Unix-style forward slashes, even on Windows. |
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|
439 |
|
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|
440 |
The Python API |
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|
441 |
~~~~~~~~~~~~~~ |
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|
442 |
|
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|
443 |
Django has two ways to load templates from files: |
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|
444 |
|
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parents:
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|
445 |
``django.template.loader.get_template(template_name)`` |
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|
446 |
``get_template`` returns the compiled template (a ``Template`` object) for |
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|
447 |
the template with the given name. If the template doesn't exist, it raises |
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|
448 |
``django.template.TemplateDoesNotExist``. |
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449 |
|
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|
450 |
``django.template.loader.select_template(template_name_list)`` |
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changeset
|
451 |
``select_template`` is just like ``get_template``, except it takes a list |
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parents:
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|
452 |
of template names. Of the list, it returns the first template that exists. |
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parents:
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changeset
|
453 |
|
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
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parents:
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changeset
|
454 |
For example, if you call ``get_template('story_detail.html')`` and have the |
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parents:
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changeset
|
455 |
above ``TEMPLATE_DIRS`` setting, here are the files Django will look for, in |
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parents:
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|
456 |
order: |
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parents:
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|
457 |
|
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parents:
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changeset
|
458 |
* ``/home/html/templates/lawrence.com/story_detail.html`` |
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parents:
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|
459 |
* ``/home/html/templates/default/story_detail.html`` |
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parents:
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changeset
|
460 |
|
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parents:
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changeset
|
461 |
If you call ``select_template(['story_253_detail.html', 'story_detail.html'])``, |
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parents:
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changeset
|
462 |
here's what Django will look for: |
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parents:
diff
changeset
|
463 |
|
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parents:
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changeset
|
464 |
* ``/home/html/templates/lawrence.com/story_253_detail.html`` |
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
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parents:
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|
465 |
* ``/home/html/templates/default/story_253_detail.html`` |
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parents:
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|
466 |
* ``/home/html/templates/lawrence.com/story_detail.html`` |
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parents:
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|
467 |
* ``/home/html/templates/default/story_detail.html`` |
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
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parents:
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changeset
|
468 |
|
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parents:
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changeset
|
469 |
When Django finds a template that exists, it stops looking. |
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parents:
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|
470 |
|
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
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parents:
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changeset
|
471 |
.. admonition:: Tip |
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
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parents:
diff
changeset
|
472 |
|
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parents:
diff
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|
473 |
You can use ``select_template()`` for super-flexible "templatability." For |
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parents:
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changeset
|
474 |
example, if you've written a news story and want some stories to have |
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
475 |
custom templates, use something like |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
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parents:
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|
476 |
``select_template(['story_%s_detail.html' % story.id, 'story_detail.html'])``. |
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Todd Larsen <tlarsen@google.com>
parents:
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changeset
|
477 |
That'll allow you to use a custom template for an individual story, with a |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
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changeset
|
478 |
fallback template for stories that don't have custom templates. |
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parents:
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|
479 |
|
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Todd Larsen <tlarsen@google.com>
parents:
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changeset
|
480 |
Using subdirectories |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
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parents:
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changeset
|
481 |
~~~~~~~~~~~~~~~~~~~~ |
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
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|
482 |
|
620f9b141567
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parents:
diff
changeset
|
483 |
It's possible -- and preferable -- to organize templates in subdirectories of |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
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changeset
|
484 |
the template directory. The convention is to make a subdirectory for each |
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parents:
diff
changeset
|
485 |
Django app, with subdirectories within those subdirectories as needed. |
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
486 |
|
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
487 |
Do this for your own sanity. Storing all templates in the root level of a |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
488 |
single directory gets messy. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
489 |
|
620f9b141567
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parents:
diff
changeset
|
490 |
To load a template that's within a subdirectory, just use a slash, like so:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
491 |
|
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
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parents:
diff
changeset
|
492 |
get_template('news/story_detail.html') |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
493 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
494 |
Using the same ``TEMPLATE_DIRS`` setting from above, this example |
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
495 |
``get_template()`` call will attempt to load the following templates: |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
496 |
|
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
497 |
* ``/home/html/templates/lawrence.com/news/story_detail.html`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
498 |
* ``/home/html/templates/default/news/story_detail.html`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
499 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
500 |
Loader types |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
501 |
~~~~~~~~~~~~ |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
502 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
503 |
By default, Django uses a filesystem-based template loader, but Django comes |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
504 |
with a few other template loaders, which know how to load templates from other |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
505 |
sources. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
506 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
507 |
These other loaders are disabled by default, but you can activate them by |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
508 |
editing your ``TEMPLATE_LOADERS`` setting. ``TEMPLATE_LOADERS`` should be a |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
509 |
tuple of strings, where each string represents a template loader. Here are the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
510 |
template loaders that come with Django: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
511 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
512 |
``django.template.loaders.filesystem.load_template_source`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
513 |
Loads templates from the filesystem, according to ``TEMPLATE_DIRS``. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
514 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
515 |
``django.template.loaders.app_directories.load_template_source`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
516 |
Loads templates from Django apps on the filesystem. For each app in |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
517 |
``INSTALLED_APPS``, the loader looks for a ``templates`` subdirectory. If |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
518 |
the directory exists, Django looks for templates in there. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
519 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
520 |
This means you can store templates with your individual apps. This also |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
521 |
makes it easy to distribute Django apps with default templates. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
522 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
523 |
For example, for this setting:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
524 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
525 |
INSTALLED_APPS = ('myproject.polls', 'myproject.music') |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
526 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
527 |
...then ``get_template('foo.html')`` will look for templates in these |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
528 |
directories, in this order: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
529 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
530 |
* ``/path/to/myproject/polls/templates/foo.html`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
531 |
* ``/path/to/myproject/music/templates/foo.html`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
532 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
533 |
Note that the loader performs an optimization when it is first imported: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
534 |
It caches a list of which ``INSTALLED_APPS`` packages have a ``templates`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
535 |
subdirectory. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
536 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
537 |
``django.template.loaders.eggs.load_template_source`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
538 |
Just like ``app_directories`` above, but it loads templates from Python |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
539 |
eggs rather than from the filesystem. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
540 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
541 |
Django uses the template loaders in order according to the ``TEMPLATE_LOADERS`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
542 |
setting. It uses each loader until a loader finds a match. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
543 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
544 |
Extending the template system |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
545 |
============================= |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
546 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
547 |
Although the Django template language comes with several default tags and |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
548 |
filters, you might want to write your own. It's easy to do. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
549 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
550 |
First, create a ``templatetags`` package in the appropriate Django app's |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
551 |
package. It should be on the same level as ``models.py``, ``views.py``, etc. For |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
552 |
example:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
553 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
554 |
polls/ |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
555 |
models.py |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
556 |
templatetags/ |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
557 |
views.py |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
558 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
559 |
Add two files to the ``templatetags`` package: an ``__init__.py`` file and a |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
560 |
file that will contain your custom tag/filter definitions. The name of the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
561 |
latter file is the name you'll use to load the tags later. For example, if your |
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
562 |
custom tags/filters are in a file called ``poll_extras.py``, you'd do the |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
563 |
following in a template:: |
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
564 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
565 |
{% load poll_extras %} |
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
566 |
|
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
567 |
The ``{% load %}`` tag looks at your ``INSTALLED_APPS`` setting and only allows |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
568 |
the loading of template libraries within installed Django apps. This is a |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
569 |
security feature: It allows you to host Python code for many template libraries |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
570 |
on a single computer without enabling access to all of them for every Django |
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
571 |
installation. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
572 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
573 |
If you write a template library that isn't tied to any particular models/views, |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
574 |
it's perfectly OK to have a Django app package that only contains a |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
575 |
``templatetags`` package. |
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
576 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
577 |
There's no limit on how many modules you put in the ``templatetags`` package. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
578 |
Just keep in mind that a ``{% load %}`` statement will load tags/filters for |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
579 |
the given Python module name, not the name of the app. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
580 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
581 |
Once you've created that Python module, you'll just have to write a bit of |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
582 |
Python code, depending on whether you're writing filters or tags. |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
583 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
584 |
To be a valid tag library, the module contain a module-level variable named |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
585 |
``register`` that is a ``template.Library`` instance, in which all the tags and |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
586 |
filters are registered. So, near the top of your module, put the following:: |
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
587 |
|
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
588 |
from django import template |
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
589 |
|
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
590 |
register = template.Library() |
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
591 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
592 |
.. admonition:: Behind the scenes |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
593 |
|
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
594 |
For a ton of examples, read the source code for Django's default filters |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
595 |
and tags. They're in ``django/template/defaultfilters.py`` and |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
596 |
``django/template/defaulttags.py``, respectively. |
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
597 |
|
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
598 |
Writing custom template filters |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
599 |
------------------------------- |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
600 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
601 |
Custom filters are just Python functions that take one or two arguments: |
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
602 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
603 |
* The value of the variable (input) -- not necessarily a string. |
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Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
604 |
* The value of the argument -- this can have a default value, or be left |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
605 |
out altogether. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
606 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
607 |
For example, in the filter ``{{ var|foo:"bar" }}``, the filter ``foo`` would be |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
608 |
passed the variable ``var`` and the argument ``"bar"``. |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
609 |
|
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
610 |
Filter functions should always return something. They shouldn't raise |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
611 |
exceptions. They should fail silently. In case of error, they should return |
620f9b141567
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Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
612 |
either the original input or an empty string -- whichever makes more sense. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
613 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
614 |
Here's an example filter definition:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
615 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
616 |
def cut(value, arg): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
617 |
"Removes all values of arg from the given string" |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
618 |
return value.replace(arg, '') |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
619 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
620 |
And here's an example of how that filter would be used:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
621 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
622 |
{{ somevariable|cut:"0" }} |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
623 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
624 |
Most filters don't take arguments. In this case, just leave the argument out of |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
625 |
your function. Example:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
626 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
627 |
def lower(value): # Only one argument. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
628 |
"Converts a string into all lowercase" |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
629 |
return value.lower() |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
630 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
631 |
When you've written your filter definition, you need to register it with |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
632 |
your ``Library`` instance, to make it available to Django's template language:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
633 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
634 |
register.filter('cut', cut) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
635 |
register.filter('lower', lower) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
636 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
637 |
The ``Library.filter()`` method takes two arguments: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
638 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
639 |
1. The name of the filter -- a string. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
640 |
2. The compilation function -- a Python function (not the name of the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
641 |
function as a string). |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
642 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
643 |
If you're using Python 2.4 or above, you can use ``register.filter()`` as a |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
644 |
decorator instead:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
645 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
646 |
@register.filter(name='cut') |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
647 |
def cut(value, arg): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
648 |
return value.replace(arg, '') |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
649 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
650 |
@register.filter |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
651 |
def lower(value): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
652 |
return value.lower() |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
653 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
654 |
If you leave off the ``name`` argument, as in the second example above, Django |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
655 |
will use the function's name as the filter name. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
656 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
657 |
Template filters which expect strings |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
658 |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
659 |
If you are writing a template filter which only expects a string as the first |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
660 |
argument, you should use the included decorator ``stringfilter`` which will convert |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
661 |
an object to it's string value before being passed to your function:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
662 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
663 |
from django import template |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
664 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
665 |
@template.stringfilter |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
666 |
def lower(value): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
667 |
return value.lower() |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
668 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
669 |
Writing custom template tags |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
670 |
---------------------------- |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
671 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
672 |
Tags are more complex than filters, because tags can do anything. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
673 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
674 |
A quick overview |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
675 |
~~~~~~~~~~~~~~~~ |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
676 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
677 |
Above, this document explained that the template system works in a two-step |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
678 |
process: compiling and rendering. To define a custom template tag, you specify |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
679 |
how the compilation works and how the rendering works. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
680 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
681 |
When Django compiles a template, it splits the raw template text into |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
682 |
''nodes''. Each node is an instance of ``django.template.Node`` and has |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
683 |
a ``render()`` method. A compiled template is, simply, a list of ``Node`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
684 |
objects. When you call ``render()`` on a compiled template object, the template |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
685 |
calls ``render()`` on each ``Node`` in its node list, with the given context. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
686 |
The results are all concatenated together to form the output of the template. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
687 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
688 |
Thus, to define a custom template tag, you specify how the raw template tag is |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
689 |
converted into a ``Node`` (the compilation function), and what the node's |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
690 |
``render()`` method does. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
691 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
692 |
Writing the compilation function |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
693 |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
694 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
695 |
For each template tag the template parser encounters, it calls a Python |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
696 |
function with the tag contents and the parser object itself. This function is |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
697 |
responsible for returning a ``Node`` instance based on the contents of the tag. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
698 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
699 |
For example, let's write a template tag, ``{% current_time %}``, that displays |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
700 |
the current date/time, formatted according to a parameter given in the tag, in |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
701 |
`strftime syntax`_. It's a good idea to decide the tag syntax before anything |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
702 |
else. In our case, let's say the tag should be used like this:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
703 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
704 |
<p>The time is {% current_time "%Y-%m-%d %I:%M %p" %}.</p> |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
705 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
706 |
.. _`strftime syntax`: http://www.python.org/doc/current/lib/module-time.html#l2h-1941 |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
707 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
708 |
The parser for this function should grab the parameter and create a ``Node`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
709 |
object:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
710 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
711 |
from django import template |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
712 |
def do_current_time(parser, token): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
713 |
try: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
714 |
# split_contents() knows not to split quoted strings. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
715 |
tag_name, format_string = token.split_contents() |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
716 |
except ValueError: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
717 |
raise template.TemplateSyntaxError, "%r tag requires a single argument" % token.contents[0] |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
718 |
if not (format_string[0] == format_string[-1] and format_string[0] in ('"', "'")): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
719 |
raise template.TemplateSyntaxError, "%r tag's argument should be in quotes" % tag_name |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
720 |
return CurrentTimeNode(format_string[1:-1]) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
721 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
722 |
Notes: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
723 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
724 |
* ``parser`` is the template parser object. We don't need it in this |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
725 |
example. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
726 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
727 |
* ``token.contents`` is a string of the raw contents of the tag. In our |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
728 |
example, it's ``'current_time "%Y-%m-%d %I:%M %p"'``. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
729 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
730 |
* The ``token.split_contents()`` method separates the arguments on spaces |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
731 |
while keeping quoted strings together. The more straightforward |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
732 |
``token.contents.split()`` wouldn't be as robust, as it would naively |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
733 |
split on *all* spaces, including those within quoted strings. It's a good |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
734 |
idea to always use ``token.split_contents()``. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
735 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
736 |
* This function is responsible for raising |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
737 |
``django.template.TemplateSyntaxError``, with helpful messages, for |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
738 |
any syntax error. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
739 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
740 |
* The ``TemplateSyntaxError`` exceptions use the ``tag_name`` variable. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
741 |
Don't hard-code the tag's name in your error messages, because that |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
742 |
couples the tag's name to your function. ``token.contents.split()[0]`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
743 |
will ''always'' be the name of your tag -- even when the tag has no |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
744 |
arguments. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
745 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
746 |
* The function returns a ``CurrentTimeNode`` with everything the node needs |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
747 |
to know about this tag. In this case, it just passes the argument -- |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
748 |
``"%Y-%m-%d %I:%M %p"``. The leading and trailing quotes from the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
749 |
template tag are removed in ``format_string[1:-1]``. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
750 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
751 |
* The parsing is very low-level. The Django developers have experimented |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
752 |
with writing small frameworks on top of this parsing system, using |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
753 |
techniques such as EBNF grammars, but those experiments made the template |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
754 |
engine too slow. It's low-level because that's fastest. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
755 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
756 |
Writing the renderer |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
757 |
~~~~~~~~~~~~~~~~~~~~ |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
758 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
759 |
The second step in writing custom tags is to define a ``Node`` subclass that |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
760 |
has a ``render()`` method. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
761 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
762 |
Continuing the above example, we need to define ``CurrentTimeNode``:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
763 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
764 |
from django import template |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
765 |
import datetime |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
766 |
class CurrentTimeNode(template.Node): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
767 |
def __init__(self, format_string): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
768 |
self.format_string = format_string |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
769 |
def render(self, context): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
770 |
return datetime.datetime.now().strftime(self.format_string) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
771 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
772 |
Notes: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
773 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
774 |
* ``__init__()`` gets the ``format_string`` from ``do_current_time()``. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
775 |
Always pass any options/parameters/arguments to a ``Node`` via its |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
776 |
``__init__()``. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
777 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
778 |
* The ``render()`` method is where the work actually happens. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
779 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
780 |
* ``render()`` should never raise ``TemplateSyntaxError`` or any other |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
781 |
exception. It should fail silently, just as template filters should. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
782 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
783 |
Ultimately, this decoupling of compilation and rendering results in an |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
784 |
efficient template system, because a template can render multiple context |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
785 |
without having to be parsed multiple times. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
786 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
787 |
Registering the tag |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
788 |
~~~~~~~~~~~~~~~~~~~ |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
789 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
790 |
Finally, register the tag with your module's ``Library`` instance, as explained |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
791 |
in "Writing custom template filters" above. Example:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
792 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
793 |
register.tag('current_time', do_current_time) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
794 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
795 |
The ``tag()`` method takes two arguments: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
796 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
797 |
1. The name of the template tag -- a string. If this is left out, the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
798 |
name of the compilation function will be used. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
799 |
2. The compilation function -- a Python function (not the name of the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
800 |
function as a string). |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
801 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
802 |
As with filter registration, it is also possible to use this as a decorator, in |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
803 |
Python 2.4 and above:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
804 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
805 |
@register.tag(name="current_time") |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
806 |
def do_current_time(parser, token): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
807 |
# ... |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
808 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
809 |
@register.tag |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
810 |
def shout(parser, token): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
811 |
# ... |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
812 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
813 |
If you leave off the ``name`` argument, as in the second example above, Django |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
814 |
will use the function's name as the tag name. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
815 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
816 |
Passing template variables to the tag |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
817 |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
818 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
819 |
Although you can pass any number of arguments to a template tag using |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
820 |
``token.split_contents()``, the arguments are all unpacked as |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
821 |
string literals. A little more work is required in order to dynamic content (a |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
822 |
template variable) to a template tag as an argument. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
823 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
824 |
While the previous examples have formatted the current time into a string and |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
825 |
returned the string, suppose you wanted to pass in a ``DateTimeField`` from an |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
826 |
object and have the template tag format that date-time:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
827 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
828 |
<p>This post was last updated at {% format_time blog_entry.date_updated "%Y-%m-%d %I:%M %p" %}.</p> |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
829 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
830 |
Initially, ``token.split_contents()`` will return three values: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
831 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
832 |
1. The tag name ``format_time``. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
833 |
2. The string "blog_entry.date_updated" (without the surrounding quotes). |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
834 |
3. The formatting string "%Y-%m-%d %I:%M %p". The return value from |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
835 |
``split_contents()`` will include the leading and trailing quotes for |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
836 |
string literals like this. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
837 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
838 |
Now your tag should begin to look like this:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
839 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
840 |
from django import template |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
841 |
def do_format_time(parser, token): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
842 |
try: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
843 |
# split_contents() knows not to split quoted strings. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
844 |
tag_name, date_to_be_formatted, format_string = token.split_contents() |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
845 |
except ValueError: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
846 |
raise template.TemplateSyntaxError, "%r tag requires exactly two arguments" % token.contents[0] |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
847 |
if not (format_string[0] == format_string[-1] and format_string[0] in ('"', "'")): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
848 |
raise template.TemplateSyntaxError, "%r tag's argument should be in quotes" % tag_name |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
849 |
return FormatTimeNode(date_to_be_formatted, format_string[1:-1]) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
850 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
851 |
You also have to change the renderer to retrieve the actual contents of the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
852 |
``date_updated`` property of the ``blog_entry`` object. This can be |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
853 |
accomplished by using the ``resolve_variable()`` function in |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
854 |
``django.template``. You pass ``resolve_variable()`` the variable name and the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
855 |
current context, available in the ``render`` method:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
856 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
857 |
from django import template |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
858 |
from django.template import resolve_variable |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
859 |
import datetime |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
860 |
class FormatTimeNode(template.Node): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
861 |
def __init__(self, date_to_be_formatted, format_string): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
862 |
self.date_to_be_formatted = date_to_be_formatted |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
863 |
self.format_string = format_string |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
864 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
865 |
def render(self, context): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
866 |
try: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
867 |
actual_date = resolve_variable(self.date_to_be_formatted, context) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
868 |
return actual_date.strftime(self.format_string) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
869 |
except VariableDoesNotExist: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
870 |
return '' |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
871 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
872 |
``resolve_variable`` will try to resolve ``blog_entry.date_updated`` and then |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
873 |
format it accordingly. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
874 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
875 |
.. note:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
876 |
The ``resolve_variable()`` function will throw a ``VariableDoesNotExist`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
877 |
exception if it cannot resolve the string passed to it in the current |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
878 |
context of the page. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
879 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
880 |
Shortcut for simple tags |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
881 |
~~~~~~~~~~~~~~~~~~~~~~~~ |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
882 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
883 |
Many template tags take a number of arguments -- strings or a template variables |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
884 |
-- and return a string after doing some processing based solely on |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
885 |
the input argument and some external information. For example, the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
886 |
``current_time`` tag we wrote above is of this variety: we give it a format |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
887 |
string, it returns the time as a string. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
888 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
889 |
To ease the creation of the types of tags, Django provides a helper function, |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
890 |
``simple_tag``. This function, which is a method of |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
891 |
``django.template.Library``, takes a function that accepts any number of |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
892 |
arguments, wraps it in a ``render`` function and the other necessary bits |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
893 |
mentioned above and registers it with the template system. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
894 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
895 |
Our earlier ``current_time`` function could thus be written like this:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
896 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
897 |
def current_time(format_string): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
898 |
return datetime.datetime.now().strftime(format_string) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
899 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
900 |
register.simple_tag(current_time) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
901 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
902 |
In Python 2.4, the decorator syntax also works:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
903 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
904 |
@register.simple_tag |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
905 |
def current_time(token): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
906 |
... |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
907 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
908 |
A couple of things to note about the ``simple_tag`` helper function: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
909 |
* Checking for the required number of arguments, etc, has already been |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
910 |
done by the time our function is called, so we don't need to do that. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
911 |
* The quotes around the argument (if any) have already been stripped away, |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
912 |
so we just receive a plain string. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
913 |
* If the argument was a template variable, our function is passed the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
914 |
current value of the variable, not the variable itself. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
915 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
916 |
When your template tag does not need access to the current context, writing a |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
917 |
function to work with the input values and using the ``simple_tag`` helper is |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
918 |
the easiest way to create a new tag. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
919 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
920 |
Inclusion tags |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
921 |
~~~~~~~~~~~~~~ |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
922 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
923 |
Another common type of template tag is the type that displays some data by |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
924 |
rendering *another* template. For example, Django's admin interface uses custom |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
925 |
template tags to display the buttons along the bottom of the "add/change" form |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
926 |
pages. Those buttons always look the same, but the link targets change depending |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
927 |
on the object being edited -- so they're a perfect case for using a small |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
928 |
template that is filled with details from the current object. (In the admin's |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
929 |
case, this is the ``submit_row`` tag.) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
930 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
931 |
These sorts of tags are called `inclusion tags`. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
932 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
933 |
Writing inclusion tags is probably best demonstrated by example. Let's write a |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
934 |
tag that outputs a list of choices for a given ``Poll`` object, such as was |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
935 |
created in the tutorials_. We'll use the tag like this:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
936 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
937 |
{% show_results poll %} |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
938 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
939 |
...and the output will be something like this:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
940 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
941 |
<ul> |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
942 |
<li>First choice</li> |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
943 |
<li>Second choice</li> |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
944 |
<li>Third choice</li> |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
945 |
</ul> |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
946 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
947 |
First, define the function that takes the argument and produces a dictionary of |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
948 |
data for the result. The important point here is we only need to return a |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
949 |
dictionary, not anything more complex. This will be used as a template context |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
950 |
for the template fragment. Example:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
951 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
952 |
def show_results(poll): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
953 |
choices = poll.choice_set.all() |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
954 |
return {'choices': choices} |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
955 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
956 |
Next, create the template used to render the tag's output. This template is a |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
957 |
fixed feature of the tag: the tag writer specifies it, not the template |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
958 |
designer. Following our example, the template is very simple:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
959 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
960 |
<ul> |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
961 |
{% for choice in choices %} |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
962 |
<li> {{ choice }} </li> |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
963 |
{% endfor %} |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
964 |
</ul> |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
965 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
966 |
Now, create and register the inclusion tag by calling the ``inclusion_tag()`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
967 |
method on a ``Library`` object. Following our example, if the above template is |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
968 |
in a file called ``results.html`` in a directory that's searched by the template |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
969 |
loader, we'd register the tag like this:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
970 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
971 |
# Here, register is a django.template.Library instance, as before |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
972 |
register.inclusion_tag('results.html')(show_results) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
973 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
974 |
As always, Python 2.4 decorator syntax works as well, so we could have |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
975 |
written:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
976 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
977 |
@register.inclusion_tag('results.html') |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
978 |
def show_results(poll): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
979 |
... |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
980 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
981 |
...when first creating the function. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
982 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
983 |
Sometimes, your inclusion tags might require a large number of arguments, |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
984 |
making it a pain for template authors to pass in all the arguments and remember |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
985 |
their order. To solve this, Django provides a ``takes_context`` option for |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
986 |
inclusion tags. If you specify ``takes_context`` in creating a template tag, |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
987 |
the tag will have no required arguments, and the underlying Python function |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
988 |
will have one argument -- the template context as of when the tag was called. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
989 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
990 |
For example, say you're writing an inclusion tag that will always be used in a |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
991 |
context that contains ``home_link`` and ``home_title`` variables that point |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
992 |
back to the main page. Here's what the Python function would look like:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
993 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
994 |
# The first argument *must* be called "context" here. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
995 |
def jump_link(context): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
996 |
return { |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
997 |
'link': context['home_link'], |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
998 |
'title': context['home_title'], |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
999 |
} |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1000 |
# Register the custom tag as an inclusion tag with takes_context=True. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1001 |
register.inclusion_tag('link.html', takes_context=True)(jump_link) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1002 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1003 |
(Note that the first parameter to the function *must* be called ``context``.) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1004 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1005 |
In that ``register.inclusion_tag()`` line, we specified ``takes_context=True`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1006 |
and the name of the template. Here's what the template ``link.html`` might look |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1007 |
like:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1008 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1009 |
Jump directly to <a href="{{ link }}">{{ title }}</a>. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1010 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1011 |
Then, any time you want to use that custom tag, load its library and call it |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1012 |
without any arguments, like so:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1013 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1014 |
{% jump_link %} |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1015 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1016 |
Note that when you're using ``takes_context=True``, there's no need to pass |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1017 |
arguments to the template tag. It automatically gets access to the context. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1018 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1019 |
The ``takes_context`` parameter defaults to ``False``. When it's set to *True*, |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1020 |
the tag is passed the context object, as in this example. That's the only |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1021 |
difference between this case and the previous ``inclusion_tag`` example. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1022 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1023 |
.. _tutorials: ../tutorial1/#creating-models |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1024 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1025 |
Setting a variable in the context |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1026 |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1027 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1028 |
The above example simply output a value. Generally, it's more flexible if your |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1029 |
template tags set template variables instead of outputting values. That way, |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1030 |
template authors can reuse the values that your template tags create. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1031 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1032 |
To set a variable in the context, just use dictionary assignment on the context |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1033 |
object in the ``render()`` method. Here's an updated version of |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1034 |
``CurrentTimeNode`` that sets a template variable ``current_time`` instead of |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1035 |
outputting it:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1036 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1037 |
class CurrentTimeNode2(template.Node): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1038 |
def __init__(self, format_string): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1039 |
self.format_string = format_string |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1040 |
def render(self, context): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1041 |
context['current_time'] = datetime.datetime.now().strftime(self.format_string) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1042 |
return '' |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1043 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1044 |
Note that ``render()`` returns the empty string. ``render()`` should always |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1045 |
return string output. If all the template tag does is set a variable, |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1046 |
``render()`` should return the empty string. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1047 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1048 |
Here's how you'd use this new version of the tag:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1049 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1050 |
{% current_time "%Y-%M-%d %I:%M %p" %}<p>The time is {{ current_time }}.</p> |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1051 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1052 |
But, there's a problem with ``CurrentTimeNode2``: The variable name |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1053 |
``current_time`` is hard-coded. This means you'll need to make sure your |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1054 |
template doesn't use ``{{ current_time }}`` anywhere else, because the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1055 |
``{% current_time %}`` will blindly overwrite that variable's value. A cleaner |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1056 |
solution is to make the template tag specify the name of the output variable, |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1057 |
like so:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1058 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1059 |
{% get_current_time "%Y-%M-%d %I:%M %p" as my_current_time %} |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1060 |
<p>The current time is {{ my_current_time }}.</p> |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1061 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1062 |
To do that, you'll need to refactor both the compilation function and ``Node`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1063 |
class, like so:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1064 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1065 |
class CurrentTimeNode3(template.Node): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1066 |
def __init__(self, format_string, var_name): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1067 |
self.format_string = format_string |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1068 |
self.var_name = var_name |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1069 |
def render(self, context): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1070 |
context[self.var_name] = datetime.datetime.now().strftime(self.format_string) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1071 |
return '' |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1072 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1073 |
import re |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1074 |
def do_current_time(parser, token): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1075 |
# This version uses a regular expression to parse tag contents. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1076 |
try: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1077 |
# Splitting by None == splitting by spaces. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1078 |
tag_name, arg = token.contents.split(None, 1) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1079 |
except ValueError: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1080 |
raise template.TemplateSyntaxError, "%r tag requires arguments" % token.contents[0] |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1081 |
m = re.search(r'(.*?) as (\w+)', arg) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1082 |
if not m: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1083 |
raise template.TemplateSyntaxError, "%r tag had invalid arguments" % tag_name |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1084 |
format_string, var_name = m.groups() |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1085 |
if not (format_string[0] == format_string[-1] and format_string[0] in ('"', "'")): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1086 |
raise template.TemplateSyntaxError, "%r tag's argument should be in quotes" % tag_name |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1087 |
return CurrentTimeNode3(format_string[1:-1], var_name) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1088 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1089 |
The difference here is that ``do_current_time()`` grabs the format string and |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1090 |
the variable name, passing both to ``CurrentTimeNode3``. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1091 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1092 |
Parsing until another block tag |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1093 |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1094 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1095 |
Template tags can work in tandem. For instance, the standard ``{% comment %}`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1096 |
tag hides everything until ``{% endcomment %}``. To create a template tag such |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1097 |
as this, use ``parser.parse()`` in your compilation function. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1098 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1099 |
Here's how the standard ``{% comment %}`` tag is implemented:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1100 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1101 |
def do_comment(parser, token): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1102 |
nodelist = parser.parse(('endcomment',)) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1103 |
parser.delete_first_token() |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1104 |
return CommentNode() |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1105 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1106 |
class CommentNode(template.Node): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1107 |
def render(self, context): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1108 |
return '' |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1109 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1110 |
``parser.parse()`` takes a tuple of names of block tags ''to parse until''. It |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1111 |
returns an instance of ``django.template.NodeList``, which is a list of |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1112 |
all ``Node`` objects that the parser encountered ''before'' it encountered |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1113 |
any of the tags named in the tuple. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1114 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1115 |
In ``"nodelist = parser.parse(('endcomment',))"`` in the above example, |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1116 |
``nodelist`` is a list of all nodes between the ``{% comment %}`` and |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1117 |
``{% endcomment %}``, not counting ``{% comment %}`` and ``{% endcomment %}`` |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1118 |
themselves. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1119 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1120 |
After ``parser.parse()`` is called, the parser hasn't yet "consumed" the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1121 |
``{% endcomment %}`` tag, so the code needs to explicitly call |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1122 |
``parser.delete_first_token()``. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1123 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1124 |
``CommentNode.render()`` simply returns an empty string. Anything between |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1125 |
``{% comment %}`` and ``{% endcomment %}`` is ignored. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1126 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1127 |
Parsing until another block tag, and saving contents |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1128 |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1129 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1130 |
In the previous example, ``do_comment()`` discarded everything between |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1131 |
``{% comment %}`` and ``{% endcomment %}``. Instead of doing that, it's |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1132 |
possible to do something with the code between block tags. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1133 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1134 |
For example, here's a custom template tag, ``{% upper %}``, that capitalizes |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1135 |
everything between itself and ``{% endupper %}``. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1136 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1137 |
Usage:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1138 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1139 |
{% upper %}This will appear in uppercase, {{ your_name }}.{% endupper %} |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1140 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1141 |
As in the previous example, we'll use ``parser.parse()``. But this time, we |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1142 |
pass the resulting ``nodelist`` to the ``Node``:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1143 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1144 |
def do_upper(parser, token): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1145 |
nodelist = parser.parse(('endupper',)) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1146 |
parser.delete_first_token() |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1147 |
return UpperNode(nodelist) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1148 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1149 |
class UpperNode(template.Node): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1150 |
def __init__(self, nodelist): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1151 |
self.nodelist = nodelist |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1152 |
def render(self, context): |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1153 |
output = self.nodelist.render(context) |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1154 |
return output.upper() |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1155 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1156 |
The only new concept here is the ``self.nodelist.render(context)`` in |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1157 |
``UpperNode.render()``. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1158 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1159 |
For more examples of complex rendering, see the source code for ``{% if %}``, |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1160 |
``{% for %}``, ``{% ifequal %}`` and ``{% ifchanged %}``. They live in |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1161 |
``django/template/defaulttags.py``. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1162 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1163 |
.. _configuration: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1164 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1165 |
Configuring the template system in standalone mode |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1166 |
================================================== |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1167 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1168 |
.. note:: |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1169 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1170 |
This section is only of interest to people trying to use the template |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1171 |
system as an output component in another application. If you're using the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1172 |
template system as part of a Django application, nothing here applies to |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1173 |
you. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1174 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1175 |
Normally, Django will load all the configuration information it needs from its |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1176 |
own default configuration file, combined with the settings in the module given |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1177 |
in the ``DJANGO_SETTINGS_MODULE`` environment variable. But if you're using the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1178 |
template system independently of the rest of Django, the environment variable |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1179 |
approach isn't very convenient, because you probably want to configure the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1180 |
template system in line with the rest of your application rather than dealing |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1181 |
with settings files and pointing to them via environment variables. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1182 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1183 |
To solve this problem, you need to use the manual configuration option |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1184 |
described in the `settings file`_ documentation. Simply import the appropriate |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1185 |
pieces of the templating system and then, *before* you call any of the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1186 |
templating functions, call ``django.conf.settings.configure()`` with any |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1187 |
settings you wish to specify. You might want to consider setting at least |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1188 |
``TEMPLATE_DIRS`` (if you're going to use template loaders), |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1189 |
``DEFAULT_CHARSET`` (although the default of ``utf-8`` is probably fine) and |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1190 |
``TEMPLATE_DEBUG``. All available settings are described in the |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1191 |
`settings documentation`_, and any setting starting with *TEMPLATE_* |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1192 |
is of obvious interest. |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1193 |
|
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1194 |
.. _settings file: ../settings/#using-settings-without-the-django-settings-module-environment-variable |
620f9b141567
Load ../../google_appengine into trunk/thirdparty/google_appengine.
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
1195 |
.. _settings documentation: ../settings/ |