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Added docs for form_for_model and form_for_instance, and added a fiel…

…ds argument so it is easy to create forms from a subset of model fields.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@5202 bcc190cf-cafb-0310-a4f2-bffc1f526a37
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commit 6aa5091d58d4f9ad18601b56d39d0de5af094f52 1 parent ca5e12b
@freakboy3742 freakboy3742 authored
View
47 django/newforms/models.py
@@ -12,17 +12,7 @@
__all__ = ('save_instance', 'form_for_model', 'form_for_instance', 'form_for_fields',
'ModelChoiceField', 'ModelMultipleChoiceField')
-def model_save(self, commit=True):
- """
- Creates and returns model instance according to self.clean_data.
-
- This method is created for any form_for_model Form.
- """
- if self.errors:
- raise ValueError("The %s could not be created because the data didn't validate." % self._model._meta.object_name)
- return save_instance(self, self._model(), commit)
-
-def save_instance(form, instance, commit=True):
+def save_instance(form, instance, fields=None, fail_message='saved', commit=True):
"""
Saves bound Form ``form``'s clean_data into model instance ``instance``.
@@ -33,15 +23,19 @@ def save_instance(form, instance, commit=True):
from django.db import models
opts = instance.__class__._meta
if form.errors:
- raise ValueError("The %s could not be changed because the data didn't validate." % opts.object_name)
+ raise ValueError("The %s could not be %s because the data didn't validate." % (opts.object_name, fail_message))
clean_data = form.clean_data
for f in opts.fields:
if not f.editable or isinstance(f, models.AutoField) or not f.name in clean_data:
continue
+ if fields and f.name not in fields:
+ continue
setattr(instance, f.name, clean_data[f.name])
if commit:
instance.save()
for f in opts.many_to_many:
+ if fields and f.name not in fields:
+ continue
if f.name in clean_data:
setattr(instance, f.attname, clean_data[f.name])
# GOTCHA: If many-to-many data is given and commit=False, the many-to-many
@@ -50,13 +44,19 @@ def save_instance(form, instance, commit=True):
# exception in that case.
return instance
-def make_instance_save(instance):
- "Returns the save() method for a form_for_instance Form."
+def make_model_save(model, fields, fail_message):
+ "Returns the save() method for a Form."
def save(self, commit=True):
- return save_instance(self, instance, commit)
+ return save_instance(self, model(), fields, fail_message, commit)
+ return save
+
+def make_instance_save(instance, fields, fail_message):
+ "Returns the save() method for a Form."
+ def save(self, commit=True):
+ return save_instance(self, instance, fields, fail_message, commit)
return save
-def form_for_model(model, form=BaseForm, formfield_callback=lambda f: f.formfield()):
+def form_for_model(model, form=BaseForm, fields=None, formfield_callback=lambda f: f.formfield()):
"""
Returns a Form class for the given Django model class.
@@ -71,13 +71,16 @@ def form_for_model(model, form=BaseForm, formfield_callback=lambda f: f.formfiel
for f in opts.fields + opts.many_to_many:
if not f.editable:
continue
+ if fields and not f.name in fields:
+ continue
formfield = formfield_callback(f)
if formfield:
field_list.append((f.name, formfield))
- fields = SortedDictFromList(field_list)
- return type(opts.object_name + 'Form', (form,), {'base_fields': fields, '_model': model, 'save': model_save})
+ base_fields = SortedDictFromList(field_list)
+ return type(opts.object_name + 'Form', (form,),
+ {'base_fields': base_fields, '_model': model, 'save': make_model_save(model, fields, 'created')})
-def form_for_instance(instance, form=BaseForm, formfield_callback=lambda f, **kwargs: f.formfield(**kwargs)):
+def form_for_instance(instance, form=BaseForm, fields=None, formfield_callback=lambda f, **kwargs: f.formfield(**kwargs)):
"""
Returns a Form class for the given Django model instance.
@@ -94,13 +97,15 @@ def form_for_instance(instance, form=BaseForm, formfield_callback=lambda f, **kw
for f in opts.fields + opts.many_to_many:
if not f.editable:
continue
+ if fields and not f.name in fields:
+ continue
current_value = f.value_from_object(instance)
formfield = formfield_callback(f, initial=current_value)
if formfield:
field_list.append((f.name, formfield))
- fields = SortedDictFromList(field_list)
+ base_fields = SortedDictFromList(field_list)
return type(opts.object_name + 'InstanceForm', (form,),
- {'base_fields': fields, '_model': model, 'save': make_instance_save(instance)})
+ {'base_fields': base_fields, '_model': model, 'save': make_instance_save(instance, fields, 'changed')})
def form_for_fields(field_list):
"Returns a Form class for the given list of Django database field instances."
View
155 docs/newforms.txt
@@ -870,6 +870,161 @@ custom ``Field`` classes. To do this, just create a subclass of
mentioned above (``required``, ``label``, ``initial``, ``widget``,
``help_text``).
+Generating forms for models
+===========================
+
+Although you can build customized forms by specifying the fields manually,
+in many cases you won't need to. Django provides helper methods to simplify the
+common cases of form creation.
+
+``form_for_model()``
+--------------------
+
+This method creates a form based upon the definition for a specific model.
+``form_for_model()`` examines the model definition, and creates a new form
+class that contains a form field for each model field that is defined.
+
+The type of fields produced on the generated form is determined by the type
+of the model fields. For example, a ``CharField`` on a model will be
+represented with a ``CharField`` on the form. Each ``ManyToManyField``
+on the model will be represented with a ``MultipleChoiceField`` on the
+form. Each ``ForeignKey`` will be represented with a ``ChoiceField``.
+A ``ChoiceField`` is also used for any model field that has a ``choices``
+attribute specified.
+
+``form_for_model()`` returns a generated class. This class must then be
+instantiated::
+
+ # Create the form class
+ >>> ArticleForm = form_for_model(Article)
+
+ # Create an empty form instance
+ >>> f = ArticleForm()
+
+The form produced by ``form_for_model`` also has a ``save()`` method. Once the
+form contains valid data, the ``save()`` method can be used to create a model
+instance with the attribute values described on the form::
+
+ # Create a form instance populated with POST data
+ >>> f = ArticleForm(request.POST)
+
+ # Save the new instance
+ >>> new_article = f.save()
+
+Using an alternate base class
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+If you want to add other methods to the generated form, you can put those
+methods onto a base class, and instruct ``form_for_model()`` to use that
+base class.
+
+By default, every form produced by ``form_for_model()`` extends
+``django.newforms.forms.BaseForm``. However, if you provide a ``forms``
+argument to ``form_for_model()``, Django will use that class as the base
+for the form it generates::
+
+ # Create the new base class:
+ >>> class MyBase(BaseForm):
+ ... def fiddle(self):
+ ... # Do whatever the method does
+
+ # Create the form class with a different base class
+ >>> ArticleForm = form_for_model(Article, form=MyBase)
+
+ # Instantiate the form
+ >>> f = ArticleForm()
+
+ # Use the base class method
+ >>> f.fiddle()
+
+Putting a subset of fields on the form
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+**New in Django development version**
+
+In some cases, you may not want all the model fields to appear on the form.
+One option is to set ``editable=False`` on the model field. ``form_for_model()``
+will not include any non-editable fields on a generated form instance.
+
+However, if you just want to exclude a field from one specific form, you
+can use the ``fields`` argument. If you provide a fields argument to
+``form_for_model()``, only the fields named will be included on the form.
+For example, if you only want the 'title' and 'pub_date' attributes to be
+included on the Article form, you would call::
+
+ >>> PartialArticleForm = form_for_model(Article, fields=('title', 'pub_date'))
+
+.. note::
+ If you specify ``fields`` when creating a form with ``form_for_model()``
+ make sure that the fields that are *not* specified can provide default
+ values, or are allowed to have a value of ``None``. If a field isn't
+ specified on a form, the object created from the form can't provide
+ a value for that attribute, which will prevent the new instance from
+ being saved.
+
+Overriding the default field types
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Although the form field types generated by ``form_for_model()`` are suitable
+for most general purposes, you may have need to override the default field
+types on a specific form. In order to do this, ``form_for_model()`` provides
+access to the *formfield callback*.
+
+The formfield callback is a function that, when provided with a model field,
+returns a form field instance. When constructing a form, ``form_for_model()``
+asks the formfield callback to provide form field types. The default
+implementation asks the model field for an appropriate field type; however,
+any other strategy may be employed. If you need to use an alternate strategy,
+you can define your own callback, and provide it to ``form_for_model()`` using
+the ``formfield_callback`` argument.
+
+For example, if you wanted to use ``MyDateFormField`` for any ``DateField``
+fields on the model, you could define the callback::
+
+ >>> def my_fields(field, **kwargs):
+ ... if isinstance(field, models.DateField):
+ ... return MyDateFormField(**kwargs)
+ ... else:
+ ... return field.formfield(**kwargs)
+
+ >>> ArticleForm = form_for_model(formfield_callback=my_fields)
+
+Note that your callback needs to handle *all* possible model field types, not
+just the ones that you want to behave differently to the default.
+
+Finding the model associated with a form
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The model class that was used to construct the form is available
+using the ``_model`` property of the generated form.
+
+``form_for_instance()``
+-----------------------
+
+``form_for_instance()`` is very similar to ``form_for_model()``. However,
+rather than using a model class to generate a form, it uses an instance of a
+model::
+
+ # Create an article
+ >>> art = Article(... some data ...)
+ >>> art.save()
+
+ # Create a form
+ >>> ArticleForm = form_for_instance(art)
+
+ # Instantiate the form
+ >>> f = ArticleForm()
+
+When a form created by ``form_for_instance()`` is created, the initial
+data values for the form fields are drawn from the instance. However,
+this data is not bound to the form. You will need to bind data to the
+form before the form can be saved.
+
+When you call ``save()`` on a form created by ``form_for_instance()``,
+the database instance will be updated.
+
+``form_for_instance()`` has ``form``, ``fields`` and ``formfield_callback``
+arguments that behave the same way as they do for ``form_for_model()``.
+
More coming soon
================
View
30 tests/modeltests/model_forms/models.py
@@ -179,6 +179,18 @@ def __str__(self):
<option value="3">Third test</option>
</select><br /> Hold down "Control", or "Command" on a Mac, to select more than one.</td></tr>
+You can restrict a form to a subset of the complete list of fields
+by providing a 'fields' argument. If you try to save a
+model created with such a form, you need to ensure that the fields
+that are _not_ on the form have default values, or are allowed to have
+a value of None. If a field isn't specified on a form, the object created
+from the form can't provide a value for that field!
+>>> PartialArticleForm = form_for_model(Article, fields=('headline','pub_date'))
+>>> f = PartialArticleForm(auto_id=False)
+>>> print f
+<tr><th>Headline:</th><td><input type="text" name="headline" maxlength="50" /></td></tr>
+<tr><th>Pub date:</th><td><input type="text" name="pub_date" /></td></tr>
+
You can pass a custom Form class to form_for_model. Make sure it's a
subclass of BaseForm, not Form.
>>> class CustomForm(BaseForm):
@@ -224,7 +236,23 @@ def __str__(self):
<option value="2">It&#39;s a test</option>
<option value="3">Third test</option>
</select> Hold down "Control", or "Command" on a Mac, to select more than one.</li>
->>> f = TestArticleForm({'headline': u'New headline', 'pub_date': u'1988-01-04', 'writer': u'1', 'article': 'Hello.'})
+>>> f = TestArticleForm({'headline': u'Test headline', 'pub_date': u'1984-02-06', 'writer': u'1', 'article': 'Hello.'})
+>>> f.is_valid()
+True
+>>> test_art = f.save()
+>>> test_art.id
+1
+>>> test_art = Article.objects.get(id=1)
+>>> test_art.headline
+'Test headline'
+
+You can create a form over a subset of the available fields
+by specifying a 'fields' argument to form_for_instance.
+>>> PartialArticleForm = form_for_instance(art, fields=('headline','pub_date'))
+>>> f = PartialArticleForm({'headline': u'New headline', 'pub_date': u'1988-01-04'}, auto_id=False)
+>>> print f.as_ul()
+<li>Headline: <input type="text" name="headline" value="New headline" maxlength="50" /></li>
+<li>Pub date: <input type="text" name="pub_date" value="1988-01-04" /></li>
>>> f.is_valid()
True
>>> new_art = f.save()
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