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 """Module containing enhanced db.Model classes.

    18 

    19 The classes in this module are intended to serve as base classes for all

    20 Melange Datastore Models.

    21 """

    22 

    23 __authors__ = [

    24   '"Todd Larsen" <tlarsen@google.com>',

    25 ]

    26 

    27 

    28 from google.appengine.ext import db

    29 

    30 from soc.views.helpers import forms_helpers

    31 

    32 

    33 class ModelWithFieldAttributes(db.Model):

    34   """A db.Model extension that provides access to Model properties attributes.

    35   

    36   Due to the way the Property class in Google App Engine implements __get__()

    37   and __set__(), it is not possible to access attributes of Model properties,

    38   such as verbose_name, from within a Django template.  This class works

    39   around that limitation by creating an inner Form class per Model class,

    40   since an unbound Form object contains (most of?) the property attributes

    41   attached to each corresponding Form field.

    42   

    43   Some are attributes are renamed during the conversion from a Model Property

    44   to a Form field; for example, verbose_name becomes label.  This is tolerable

    45   because any actual Form code refers to these new names, so they are should

    46   be familiar to view creators.  

    47   """

    48 

    49   _fields_cache = None

    50   

    51   @classmethod

    52   def fields(cls):

    53     """Called by the Django template engine during template instantiation.

    54     

    55     Since the attribute names use the Form fields naming instead of the

    56     Property attribute naming, accessing, for example:

    57       {{ entity.property.verbose_name }}

    58     is accomplished using:

    59       {{ entity.fields.property.label }}

    60     

    61     Args:

    62       cls: Model class, so that each Model class can create its own

    63         unbound Form the first time fields() is called by the Django

    64         template engine.

    65  

    66     Returns:

    67       A (created-on-first-use) unbound Form object that can be used to

    68       access Property attributes that are not accessible from the

    69       Property itself via the Model entity.

    70     """

    71     if not cls._fields_cache or (cls != cls._fields_cache.__class__.Meta.model):

    72       class FieldsProxy(forms_helpers.DbModelForm):

    73         """Form used as a proxy to access User model properties attributes.

    74         """

    75       

    76         class Meta:

    77           """Inner Meta class that pairs the User Model with this "form".

    78           """

    79           #: db.Model subclass for which to access model properties attributes

    80           model = cls

    81       

    82       cls._fields_cache = FieldsProxy()

    83 

    84     return cls._fields_cache