1 #!/usr/bin/python2.5

     2 #

     3 # Copyright 2008 the Melange authors.

     4 #

     5 # Licensed under the Apache License, Version 2.0 (the "License");

     6 # you may not use this file except in compliance with the License.

     7 # You may obtain a copy of the License at

     8 #

     9 #   http://www.apache.org/licenses/LICENSE-2.0

    10 #

    11 # Unless required by applicable law or agreed to in writing, software

    12 # distributed under the License is distributed on an "AS IS" BASIS,

    13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

    14 # See the License for the specific language governing permissions and

    15 # limitations under the License.

    16 

    17 """This module defines classes and functions for Dynamic Forms

    18 """

    19 

    20 __authors__ = [

    21     '"Sverre Rabbelier" <sverre@rabbelier.nl>',

    22     ]

    23 

    24 

    25 from google.appengine.ext.db import djangoforms

    26 

    27 from soc.logic import dicts

    28 

    29 

    30 class DynaFormMetaclass(djangoforms.ModelFormMetaclass):

    31   """The DynaForm Meta class, adding support for dynamically defined fields

    32 

    33   The new DynaForm class that is created by class function is very

    34   similar to one created by the regular djangoforms.ModelFormMetaclass.

    35   The only difference is that is the form class has a Meta property,

    36   it's 'dynaconf' field will be used to define additional properties

    37   in the form class.

    38 

    39   The 'dynaconf' field (if present), is expected to be iterable as a

    40   dictionary (with iteritems). The keys are used as the property names,

    41   and the values are used as the property value.

    42   """

    43 

    44   def __new__(cls, class_name, bases, attrs):

    45     """See djangoforms.ModelFormMetaclass on how the __new__ method

    46     is used, for an explanation on how this class modifies the default

    47     behavior, see the DynaFormMetaclass's docstring.

    48     """

    49 

    50     # Retrieve the Meta class, if present

    51     meta = attrs.get('Meta', None)

    52     conf = None

    53 

    54     # Try to retrieve the dynaconf property

    55     if meta:

    56       conf = getattr(meta, 'dynaconf', None)

    57 

    58     # When found, extend the form's attribute's with the specified ones

    59     if conf:

    60       for key, value in conf.iteritems():

    61         attrs[key] = value

    62 

    63     # Leave the rest to djangoforms.ModelFormMetaclass.

    64     return super(DynaFormMetaclass, cls).__new__(cls, class_name, bases, attrs)

    65 

    66 

    67 def newDynaForm(dynamodel=None, dynabase=None, dynainclude=None, 

    68                 dynaexclude=None, dynafields=None):

    69   """Creates a new form DynaForm class

    70 

    71   The returned class extends dynabase, but with the following additions:

    72   * It has a Meta class with the 'model', 'include', and 'exclude'

    73   fields set as specified by newDynaForm's keyword arguments.

    74   * It's __metaclass__ is set to DynaFormMetaclass (which inherits from

    75   the default djangoforms.ModelFormMetaclass).

    76   * The Meta class has an additional dynaconf field which is set to

    77   the dyanfields keyword argument passed to newDynaForm.

    78 

    79   See DynaFormMetaclass for an explanation on how the dynafields

    80   property is used to construct the DynaForm class.

    81   """

    82 

    83   class DynaForm(dynabase):

    84     """The dynamically created Form class

    85     """

    86 

    87     __metaclass__ = DynaFormMetaclass

    88 

    89     class Meta:

    90       """Inner Meta class that defines some behavior for the form.

    91       """

    92 

    93       model = dynamodel

    94       include = dynainclude

    95       exclude = dynaexclude

    96       dynaconf = dynafields

    97 

    98   return DynaForm

    99 

   100 

   101 def extendDynaForm(dynaform, dynainclude=None, dynaexclude=None, dynafields=None):

   102   """Extends an existing dynaform

   103 

   104   If any of dynainclude, dynaexclude or dynafields are not present,

   105   they are retrieved from dynaform (if present in it's Meta class).

   106 

   107   While it is rather useles to extend from a dynaform that does not have

   108   a Meta class, it is allowed, the resulting DynaForm is the same as if

   109   newDynaForm was called with all extendDynForm's keyword arguments.

   110   """

   111 

   112   # Try to retrieve the Meta class from the existing dynaform

   113   meta = getattr(dynaform, 'Meta', None)

   114 

   115   # If we find one, we can use it to 'extend' from

   116   if meta:

   117     dynamodel = getattr(meta, 'model', None)

   118 

   119     if not dynainclude:

   120       dynainclude = getattr(meta, 'include', None)

   121 

   122     if not dynaexclude:

   123       dynaexclude = getattr(meta, 'exclude', None)

   124 

   125     # The most intersting parameter, the 'extra fields' dictionary

   126     dynaconf = getattr(meta, 'dynaconf', {})

   127     if not dynafields:

   128       dynafields = dynaconf

   129     else:

   130       dicts.merge(dynafields, dynaconf)

   131 

   132   # Create a new DynaForm, using the properties we extracted

   133   return newDynaForm(

   134       dynamodel=dynamodel,

   135       dynabase=dynaform,

   136       dynainclude=dynainclude,

   137       dynaexclude=dynaexclude,

   138       dynafields=dynafields)