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Modified [7112] to make things behave more in line with Python subcla…

…ssing when subclassing ModelForms.

Meta can now be subclassed and changes on the child model affect the fields
list. Also removed a block of error checking, since it's harder to mess up in
unexpected ways now (e.g. you can't change the model and get the entirely wrong
fields list), so it was a level of overkill.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@7115 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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commit 1159791cd5b706f01e282d6773a17b66b7cdac9f 1 parent 37962ec
@malcolmt malcolmt authored
View
22 django/newforms/forms.py
@@ -22,16 +22,30 @@ def pretty_name(name):
name = name[0].upper() + name[1:]
return name.replace('_', ' ')
-def get_declared_fields(bases, attrs):
+def get_declared_fields(bases, attrs, with_base_fields=True):
+ """
+ Create a list of form field instances from the passed in 'attrs', plus any
+ similar fields on the base classes (in 'bases'). This is used by both the
+ Form and ModelForm metclasses.
+
+ If 'with_base_fields' is True, all fields from the bases are used.
+ Otherwise, only fields in the 'declared_fields' attribute on the bases are
+ used. The distinction is useful in ModelForm subclassing.
+ """
fields = [(field_name, attrs.pop(field_name)) for field_name, obj in attrs.items() if isinstance(obj, Field)]
fields.sort(lambda x, y: cmp(x[1].creation_counter, y[1].creation_counter))
# If this class is subclassing another Form, add that Form's fields.
# Note that we loop over the bases in *reverse*. This is necessary in
# order to preserve the correct order of fields.
- for base in bases[::-1]:
- if hasattr(base, 'base_fields'):
- fields = base.base_fields.items() + fields
+ if with_base_fields:
+ for base in bases[::-1]:
+ if hasattr(base, 'base_fields'):
+ fields = base.base_fields.items() + fields
+ else:
+ for base in bases[::-1]:
+ if hasattr(base, 'declared_fields'):
+ fields = base.declared_fields.items() + fields
return SortedDict(fields)
View
23 django/newforms/models.py
@@ -225,7 +225,7 @@ def __new__(cls, name, bases, attrs,
attrs)
new_class = type.__new__(cls, name, bases, attrs)
- declared_fields = get_declared_fields(bases, attrs)
+ declared_fields = get_declared_fields(bases, attrs, False)
opts = new_class._meta = ModelFormOptions(getattr(new_class, 'Meta', None))
if opts.model:
# If a model is defined, extract form fields from it.
@@ -236,27 +236,8 @@ def __new__(cls, name, bases, attrs,
fields.update(declared_fields)
else:
fields = declared_fields
+ new_class.declared_fields = declared_fields
new_class.base_fields = fields
-
- # XXX: The following is a sanity check for the user to avoid
- # inadvertent attribute hiding.
-
- # Search base classes, but don't allow more than one Meta model
- # definition. The fields would be generated correctly, but the save
- # method won't deal with more than one object. Also, it wouldn't be
- # clear what to do with multiple fields and exclude lists.
- first = None
- current = opts.model
- for base in parents:
- base_opts = getattr(base, '_meta', None)
- base_model = getattr(base_opts, 'model', None)
- if base_model:
- if current:
- if base_model is not current:
- raise ImproperlyConfigured("%s's base classes define more than one model." % name)
- else:
- current = base_model
-
return new_class
class BaseModelForm(BaseForm):
View
22 docs/modelforms.txt
@@ -335,14 +335,19 @@ models. For example, using the previous ``ArticleForm`` class::
This creates a form that behaves identically to ``ArticleForm``, except there
is some extra validation and cleaning for the ``pub_date`` field.
+You can also subclass the parent's ``Meta`` inner class if you want to change
+the ``Meta.fields`` or ``Meta.excludes`` lists::
+
+ >>> class RestrictedArticleForm(EnhancedArticleForm):
+ ... class Meta(ArticleForm.Meta):
+ ... exclude = ['body']
+
+This adds in the extra method from the ``EnhancedArticleForm`` and modifies
+the original ``ArticleForm.Meta`` to remove one field.
+
There are a couple of things to note, however. Most of these won't normally be
of concern unless you are trying to do something tricky with subclassing.
- * All the fields from the parent classes will appear in the child
- ``ModelForm``. This means you cannot change a parent's ``Meta.exclude``
- attribute, for example, and except it to have an effect, since the field is
- already part of the field list in the parent class.
-
* Normal Python name resolution rules apply. If you have multiple base
classes that declare a ``Meta`` inner class, only the first one will be
used. This means the child's ``Meta``, if it exists, otherwise the
@@ -351,10 +356,3 @@ of concern unless you are trying to do something tricky with subclassing.
* For technical reasons, you cannot have a subclass that is inherited from
both a ``ModelForm`` and a ``Form`` simultaneously.
-Because of the "child inherits all fields from parents" behaviour, you
-shouldn't try to declare model fields in multiple classes (parent and child).
-Instead, declare all the model-related stuff in one class and use inheritance
-to add "extra" non-model fields and methods to the final result. Whether you
-put the "extra" functions in the parent class or the child class will depend
-on how you intend to reuse them.
-
View
37 tests/modeltests/model_forms/models.py
@@ -155,43 +155,52 @@ def __unicode__(self):
... class Meta:
... model = Category
->>> class BadForm(CategoryForm):
+>>> class OddForm(CategoryForm):
... class Meta:
... model = Article
-Traceback (most recent call last):
-...
-ImproperlyConfigured: BadForm's base classes define more than one model.
+
+OddForm is now an Article-related thing, because BadForm.Meta overrides
+CategoryForm.Meta.
+>>> OddForm.base_fields.keys()
+['headline', 'slug', 'pub_date', 'writer', 'article', 'status', 'categories']
>>> class ArticleForm(ModelForm):
... class Meta:
... model = Article
+First class with a Meta class wins.
+
>>> class BadForm(ArticleForm, CategoryForm):
... pass
-Traceback (most recent call last):
-...
-ImproperlyConfigured: BadForm's base classes define more than one model.
+>>> OddForm.base_fields.keys()
+['headline', 'slug', 'pub_date', 'writer', 'article', 'status', 'categories']
-This one is OK since the subclass specifies the same model as the parent.
+Subclassing without specifying a Meta on the class will use the parent's Meta
+(or the first parent in the MRO if there are multiple parent classes).
->>> class SubCategoryForm(CategoryForm):
+>>> class CategoryForm(ModelForm):
... class Meta:
... model = Category
+>>> class SubCategoryForm(CategoryForm):
+... pass
+>>> SubCategoryForm.base_fields.keys()
+['name', 'slug', 'url']
-
-Subclassing without specifying a Meta on the class will use the parent's Meta
-(or the first parent in the MRO if there are multiple parent classes).
+We can also subclass the Meta inner class to change the fields list.
>>> class CategoryForm(ModelForm):
+... checkbox = forms.BooleanField()
+...
... class Meta:
... model = Category
-... exclude = ['url']
>>> class SubCategoryForm(CategoryForm):
-... pass
+... class Meta(CategoryForm.Meta):
+... exclude = ['url']
>>> print SubCategoryForm()
<tr><th><label for="id_name">Name:</label></th><td><input id="id_name" type="text" name="name" maxlength="20" /></td></tr>
<tr><th><label for="id_slug">Slug:</label></th><td><input id="id_slug" type="text" name="slug" maxlength="20" /></td></tr>
+<tr><th><label for="id_checkbox">Checkbox:</label></th><td><input type="checkbox" name="checkbox" id="id_checkbox" /></td></tr>
# Old form_for_x tests #######################################################
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