Modified [7112] to make things behave more in line with Python subclassing 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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@ -22,16 +22,30 @@ def pretty_name(name):
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name = name[0].upper() + name[1:]
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return name.replace('_', ' ')
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def get_declared_fields(bases, attrs):
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def get_declared_fields(bases, attrs, with_base_fields=True):
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"""
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Create a list of form field instances from the passed in 'attrs', plus any
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similar fields on the base classes (in 'bases'). This is used by both the
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Form and ModelForm metclasses.
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If 'with_base_fields' is True, all fields from the bases are used.
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Otherwise, only fields in the 'declared_fields' attribute on the bases are
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used. The distinction is useful in ModelForm subclassing.
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"""
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fields = [(field_name, attrs.pop(field_name)) for field_name, obj in attrs.items() if isinstance(obj, Field)]
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fields.sort(lambda x, y: cmp(x[1].creation_counter, y[1].creation_counter))
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# If this class is subclassing another Form, add that Form's fields.
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# Note that we loop over the bases in *reverse*. This is necessary in
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# order to preserve the correct order of fields.
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for base in bases[::-1]:
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if hasattr(base, 'base_fields'):
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fields = base.base_fields.items() + fields
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if with_base_fields:
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for base in bases[::-1]:
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if hasattr(base, 'base_fields'):
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fields = base.base_fields.items() + fields
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else:
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for base in bases[::-1]:
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if hasattr(base, 'declared_fields'):
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fields = base.declared_fields.items() + fields
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return SortedDict(fields)
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@ -225,7 +225,7 @@ class ModelFormMetaclass(type):
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attrs)
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new_class = type.__new__(cls, name, bases, attrs)
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declared_fields = get_declared_fields(bases, attrs)
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declared_fields = get_declared_fields(bases, attrs, False)
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opts = new_class._meta = ModelFormOptions(getattr(new_class, 'Meta', None))
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if opts.model:
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# If a model is defined, extract form fields from it.
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@ -236,27 +236,8 @@ class ModelFormMetaclass(type):
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fields.update(declared_fields)
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else:
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fields = declared_fields
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new_class.declared_fields = declared_fields
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new_class.base_fields = fields
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# XXX: The following is a sanity check for the user to avoid
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# inadvertent attribute hiding.
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# Search base classes, but don't allow more than one Meta model
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# definition. The fields would be generated correctly, but the save
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# method won't deal with more than one object. Also, it wouldn't be
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# clear what to do with multiple fields and exclude lists.
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first = None
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current = opts.model
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for base in parents:
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base_opts = getattr(base, '_meta', None)
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base_model = getattr(base_opts, 'model', None)
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if base_model:
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if current:
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if base_model is not current:
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raise ImproperlyConfigured("%s's base classes define more than one model." % name)
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else:
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current = base_model
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return new_class
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class BaseModelForm(BaseForm):
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@ -335,14 +335,19 @@ models. For example, using the previous ``ArticleForm`` class::
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This creates a form that behaves identically to ``ArticleForm``, except there
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is some extra validation and cleaning for the ``pub_date`` field.
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You can also subclass the parent's ``Meta`` inner class if you want to change
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the ``Meta.fields`` or ``Meta.excludes`` lists::
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>>> class RestrictedArticleForm(EnhancedArticleForm):
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... class Meta(ArticleForm.Meta):
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... exclude = ['body']
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This adds in the extra method from the ``EnhancedArticleForm`` and modifies
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the original ``ArticleForm.Meta`` to remove one field.
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There are a couple of things to note, however. Most of these won't normally be
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of concern unless you are trying to do something tricky with subclassing.
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* All the fields from the parent classes will appear in the child
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``ModelForm``. This means you cannot change a parent's ``Meta.exclude``
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attribute, for example, and except it to have an effect, since the field is
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already part of the field list in the parent class.
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* Normal Python name resolution rules apply. If you have multiple base
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classes that declare a ``Meta`` inner class, only the first one will be
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used. This means the child's ``Meta``, if it exists, otherwise the
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@ -351,10 +356,3 @@ of concern unless you are trying to do something tricky with subclassing.
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* For technical reasons, you cannot have a subclass that is inherited from
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both a ``ModelForm`` and a ``Form`` simultaneously.
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Because of the "child inherits all fields from parents" behaviour, you
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shouldn't try to declare model fields in multiple classes (parent and child).
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Instead, declare all the model-related stuff in one class and use inheritance
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to add "extra" non-model fields and methods to the final result. Whether you
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put the "extra" functions in the parent class or the child class will depend
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on how you intend to reuse them.
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@ -155,29 +155,25 @@ familiar with the mechanics.
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... class Meta:
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... model = Category
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>>> class BadForm(CategoryForm):
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>>> class OddForm(CategoryForm):
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... class Meta:
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... model = Article
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Traceback (most recent call last):
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...
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ImproperlyConfigured: BadForm's base classes define more than one model.
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OddForm is now an Article-related thing, because BadForm.Meta overrides
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CategoryForm.Meta.
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>>> OddForm.base_fields.keys()
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['headline', 'slug', 'pub_date', 'writer', 'article', 'status', 'categories']
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>>> class ArticleForm(ModelForm):
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... class Meta:
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... model = Article
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First class with a Meta class wins.
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>>> class BadForm(ArticleForm, CategoryForm):
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... pass
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Traceback (most recent call last):
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...
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ImproperlyConfigured: BadForm's base classes define more than one model.
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This one is OK since the subclass specifies the same model as the parent.
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>>> class SubCategoryForm(CategoryForm):
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... class Meta:
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... model = Category
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>>> OddForm.base_fields.keys()
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['headline', 'slug', 'pub_date', 'writer', 'article', 'status', 'categories']
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Subclassing without specifying a Meta on the class will use the parent's Meta
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(or the first parent in the MRO if there are multiple parent classes).
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@ -185,13 +181,26 @@ Subclassing without specifying a Meta on the class will use the parent's Meta
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>>> class CategoryForm(ModelForm):
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... class Meta:
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... model = Category
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... exclude = ['url']
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>>> class SubCategoryForm(CategoryForm):
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... pass
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>>> SubCategoryForm.base_fields.keys()
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['name', 'slug', 'url']
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We can also subclass the Meta inner class to change the fields list.
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>>> class CategoryForm(ModelForm):
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... checkbox = forms.BooleanField()
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...
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... class Meta:
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... model = Category
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>>> class SubCategoryForm(CategoryForm):
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... class Meta(CategoryForm.Meta):
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... exclude = ['url']
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>>> print SubCategoryForm()
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<tr><th><label for="id_name">Name:</label></th><td><input id="id_name" type="text" name="name" maxlength="20" /></td></tr>
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<tr><th><label for="id_slug">Slug:</label></th><td><input id="id_slug" type="text" name="slug" maxlength="20" /></td></tr>
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<tr><th><label for="id_checkbox">Checkbox:</label></th><td><input type="checkbox" name="checkbox" id="id_checkbox" /></td></tr>
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# Old form_for_x tests #######################################################
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