1149 lines
43 KiB
Plaintext
1149 lines
43 KiB
Plaintext
==========================
|
||
Creating forms from models
|
||
==========================
|
||
|
||
.. module:: django.forms.models
|
||
:synopsis: ModelForm and ModelFormset.
|
||
|
||
.. currentmodule:: django.forms
|
||
|
||
``ModelForm``
|
||
=============
|
||
.. class:: ModelForm
|
||
|
||
If you're building a database-driven app, chances are you'll have forms that
|
||
map closely to Django models. For instance, you might have a ``BlogComment``
|
||
model, and you want to create a form that lets people submit comments. In this
|
||
case, it would be redundant to define the field types in your form, because
|
||
you've already defined the fields in your model.
|
||
|
||
For this reason, Django provides a helper class that lets you create a ``Form``
|
||
class from a Django model.
|
||
|
||
For example::
|
||
|
||
>>> from django.forms import ModelForm
|
||
>>> from myapp.models import Article
|
||
|
||
# Create the form class.
|
||
>>> class ArticleForm(ModelForm):
|
||
... class Meta:
|
||
... model = Article
|
||
... fields = ['pub_date', 'headline', 'content', 'reporter']
|
||
|
||
# Creating a form to add an article.
|
||
>>> form = ArticleForm()
|
||
|
||
# Creating a form to change an existing article.
|
||
>>> article = Article.objects.get(pk=1)
|
||
>>> form = ArticleForm(instance=article)
|
||
|
||
Field types
|
||
-----------
|
||
|
||
The generated ``Form`` class will have a form field for every model field
|
||
specified, in the order specified in the ``fields`` attribute.
|
||
|
||
Each model field has a corresponding default form field. For example, a
|
||
``CharField`` on a model is represented as a ``CharField`` on a form. A model
|
||
``ManyToManyField`` is represented as a ``MultipleChoiceField``. Here is the
|
||
full list of conversions:
|
||
|
||
=============================== ========================================
|
||
Model field Form field
|
||
=============================== ========================================
|
||
``AutoField`` Not represented in the form
|
||
|
||
``BigIntegerField`` ``IntegerField`` with ``min_value`` set
|
||
to -9223372036854775808 and ``max_value``
|
||
set to 9223372036854775807.
|
||
|
||
``BooleanField`` ``BooleanField``
|
||
|
||
``CharField`` ``CharField`` with ``max_length`` set to
|
||
the model field's ``max_length``
|
||
|
||
``CommaSeparatedIntegerField`` ``CharField``
|
||
|
||
``DateField`` ``DateField``
|
||
|
||
``DateTimeField`` ``DateTimeField``
|
||
|
||
``DecimalField`` ``DecimalField``
|
||
|
||
``EmailField`` ``EmailField``
|
||
|
||
``FileField`` ``FileField``
|
||
|
||
``FilePathField`` ``FilePathField``
|
||
|
||
``FloatField`` ``FloatField``
|
||
|
||
``ForeignKey`` ``ModelChoiceField`` (see below)
|
||
|
||
``ImageField`` ``ImageField``
|
||
|
||
``IntegerField`` ``IntegerField``
|
||
|
||
``IPAddressField`` ``IPAddressField``
|
||
|
||
``GenericIPAddressField`` ``GenericIPAddressField``
|
||
|
||
``ManyToManyField`` ``ModelMultipleChoiceField`` (see
|
||
below)
|
||
|
||
``NullBooleanField`` ``CharField``
|
||
|
||
``PositiveIntegerField`` ``IntegerField``
|
||
|
||
``PositiveSmallIntegerField`` ``IntegerField``
|
||
|
||
``SlugField`` ``SlugField``
|
||
|
||
``SmallIntegerField`` ``IntegerField``
|
||
|
||
``TextField`` ``CharField`` with
|
||
``widget=forms.Textarea``
|
||
|
||
``TimeField`` ``TimeField``
|
||
|
||
``URLField`` ``URLField``
|
||
=============================== ========================================
|
||
|
||
|
||
As you might expect, the ``ForeignKey`` and ``ManyToManyField`` model field
|
||
types are special cases:
|
||
|
||
* ``ForeignKey`` is represented by ``django.forms.ModelChoiceField``,
|
||
which is a ``ChoiceField`` whose choices are a model ``QuerySet``.
|
||
|
||
* ``ManyToManyField`` is represented by
|
||
``django.forms.ModelMultipleChoiceField``, which is a
|
||
``MultipleChoiceField`` whose choices are a model ``QuerySet``.
|
||
|
||
In addition, each generated form field has attributes set as follows:
|
||
|
||
* If the model field has ``blank=True``, then ``required`` is set to
|
||
``False`` on the form field. Otherwise, ``required=True``.
|
||
|
||
* The form field's ``label`` is set to the ``verbose_name`` of the model
|
||
field, with the first character capitalized.
|
||
|
||
* The form field's ``help_text`` is set to the ``help_text`` of the model
|
||
field.
|
||
|
||
* If the model field has ``choices`` set, then the form field's ``widget``
|
||
will be set to ``Select``, with choices coming from the model field's
|
||
``choices``. The choices will normally include the blank choice which is
|
||
selected by default. If the field is required, this forces the user to
|
||
make a selection. The blank choice will not be included if the model
|
||
field has ``blank=False`` and an explicit ``default`` value (the
|
||
``default`` value will be initially selected instead).
|
||
|
||
Finally, note that you can override the form field used for a given model
|
||
field. See `Overriding the default fields`_ below.
|
||
|
||
A full example
|
||
--------------
|
||
|
||
Consider this set of models::
|
||
|
||
from django.db import models
|
||
from django.forms import ModelForm
|
||
|
||
TITLE_CHOICES = (
|
||
('MR', 'Mr.'),
|
||
('MRS', 'Mrs.'),
|
||
('MS', 'Ms.'),
|
||
)
|
||
|
||
class Author(models.Model):
|
||
name = models.CharField(max_length=100)
|
||
title = models.CharField(max_length=3, choices=TITLE_CHOICES)
|
||
birth_date = models.DateField(blank=True, null=True)
|
||
|
||
# On Python 3: def __str__(self):
|
||
def __unicode__(self):
|
||
return self.name
|
||
|
||
class Book(models.Model):
|
||
name = models.CharField(max_length=100)
|
||
authors = models.ManyToManyField(Author)
|
||
|
||
class AuthorForm(ModelForm):
|
||
class Meta:
|
||
model = Author
|
||
fields = ['name', 'title', 'birth_date']
|
||
|
||
class BookForm(ModelForm):
|
||
class Meta:
|
||
model = Book
|
||
fields = ['name', 'authors']
|
||
|
||
|
||
With these models, the ``ModelForm`` subclasses above would be roughly
|
||
equivalent to this (the only difference being the ``save()`` method, which
|
||
we'll discuss in a moment.)::
|
||
|
||
from django import forms
|
||
|
||
class AuthorForm(forms.Form):
|
||
name = forms.CharField(max_length=100)
|
||
title = forms.CharField(max_length=3,
|
||
widget=forms.Select(choices=TITLE_CHOICES))
|
||
birth_date = forms.DateField(required=False)
|
||
|
||
class BookForm(forms.Form):
|
||
name = forms.CharField(max_length=100)
|
||
authors = forms.ModelMultipleChoiceField(queryset=Author.objects.all())
|
||
|
||
.. _validation-on-modelform:
|
||
|
||
Validation on a ``ModelForm``
|
||
-----------------------------
|
||
|
||
There are two main steps involved in validating a ``ModelForm``:
|
||
|
||
1. :ref:`Validating the form <form-and-field-validation>`
|
||
2. :ref:`Validating the model instance <validating-objects>`
|
||
|
||
Just like normal form validation, model form validation is triggered implicitly
|
||
when calling :meth:`~django.forms.Form.is_valid()` or accessing the
|
||
:attr:`~django.forms.Form.errors` attribute and explicitly when calling
|
||
``full_clean()``, although you will typically not use the latter method in
|
||
practice.
|
||
|
||
``Model`` validation (:meth:`Model.full_clean()
|
||
<django.db.models.Model.full_clean()>`) is triggered from within the form
|
||
validation step, right after the form's ``clean()`` method is called.
|
||
|
||
.. warning::
|
||
|
||
The cleaning process modifies the model instance passed to the
|
||
``ModelForm`` constructor in various ways. For instance, any date fields on
|
||
the model are converted into actual date objects. Failed validation may
|
||
leave the underlying model instance in an inconsistent state and therefore
|
||
it's not recommended to reuse it.
|
||
|
||
.. _overriding-modelform-clean-method:
|
||
|
||
Overriding the clean() method
|
||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||
|
||
You can override the ``clean()`` method on a model form to provide additional
|
||
validation in the same way you can on a normal form.
|
||
|
||
A model form instance bound to a model object will contain an ``instance``
|
||
attribute that gives its methods access to that specific model instance.
|
||
|
||
.. warning::
|
||
|
||
The ``ModelForm.clean()`` method sets a flag that makes the :ref:`model
|
||
validation <validating-objects>` step validate the uniqueness of model
|
||
fields that are marked as ``unique``, ``unique_together`` or
|
||
``unique_for_date|month|year``.
|
||
|
||
If you would like to override the ``clean()`` method and maintain this
|
||
validation, you must call the parent class's ``clean()`` method.
|
||
|
||
Interaction with model validation
|
||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||
|
||
As part of the validation process, ``ModelForm`` will call the ``clean()``
|
||
method of each field on your model that has a corresponding field on your form.
|
||
If you have excluded any model fields, validation will not be run on those
|
||
fields. See the :doc:`form validation </ref/forms/validation>` documentation
|
||
for more on how field cleaning and validation work.
|
||
|
||
The model's ``clean()`` method will be called before any uniqueness checks are
|
||
made. See :ref:`Validating objects <validating-objects>` for more information
|
||
on the model's ``clean()`` hook.
|
||
|
||
Considerations regarding fields' ``error_messages``
|
||
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||
|
||
Error messages defined at the
|
||
:attr:`form field <django.forms.Field.error_messages>` level or at the
|
||
:ref:`form Meta <modelforms-overriding-default-fields>` level always take
|
||
precedence over the error messages defined at the
|
||
:attr:`model field <django.db.models.Field.error_messages>` level.
|
||
Error messages defined on :attr:`model fields
|
||
<django.db.models.Field.error_messages>` are only used when the
|
||
``ValidationError`` is raised during the :ref:`model validation
|
||
<validating-objects>` step and no corresponding error messages are defined at
|
||
the form level.
|
||
|
||
The ``save()`` method
|
||
---------------------
|
||
|
||
Every ``ModelForm`` also has a ``save()`` method. This method creates and saves
|
||
a database object from the data bound to the form. A subclass of ``ModelForm``
|
||
can accept an existing model instance as the keyword argument ``instance``; if
|
||
this is supplied, ``save()`` will update that instance. If it's not supplied,
|
||
``save()`` will create a new instance of the specified model:
|
||
|
||
.. code-block:: python
|
||
|
||
>>> from myapp.models import Article
|
||
>>> from myapp.forms import ArticleForm
|
||
|
||
# Create a form instance from POST data.
|
||
>>> f = ArticleForm(request.POST)
|
||
|
||
# Save a new Article object from the form's data.
|
||
>>> new_article = f.save()
|
||
|
||
# Create a form to edit an existing Article, but use
|
||
# POST data to populate the form.
|
||
>>> a = Article.objects.get(pk=1)
|
||
>>> f = ArticleForm(request.POST, instance=a)
|
||
>>> f.save()
|
||
|
||
Note that if the form :ref:`hasn't been validated
|
||
<validation-on-modelform>`, calling ``save()`` will do so by checking
|
||
``form.errors``. A ``ValueError`` will be raised if the data in the form
|
||
doesn't validate -- i.e., if ``form.errors`` evaluates to ``True``.
|
||
|
||
This ``save()`` method accepts an optional ``commit`` keyword argument, which
|
||
accepts either ``True`` or ``False``. If you call ``save()`` with
|
||
``commit=False``, then it will return an object that hasn't yet been saved to
|
||
the database. In this case, it's up to you to call ``save()`` on the resulting
|
||
model instance. This is useful if you want to do custom processing on the
|
||
object before saving it, or if you want to use one of the specialized
|
||
:ref:`model saving options <ref-models-force-insert>`. ``commit`` is ``True``
|
||
by default.
|
||
|
||
Another side effect of using ``commit=False`` is seen when your model has
|
||
a many-to-many relation with another model. If your model has a many-to-many
|
||
relation and you specify ``commit=False`` when you save a form, Django cannot
|
||
immediately save the form data for the many-to-many relation. This is because
|
||
it isn't possible to save many-to-many data for an instance until the instance
|
||
exists in the database.
|
||
|
||
To work around this problem, every time you save a form using ``commit=False``,
|
||
Django adds a ``save_m2m()`` method to your ``ModelForm`` subclass. After
|
||
you've manually saved the instance produced by the form, you can invoke
|
||
``save_m2m()`` to save the many-to-many form data. For example:
|
||
|
||
.. code-block:: python
|
||
|
||
# Create a form instance with POST data.
|
||
>>> f = AuthorForm(request.POST)
|
||
|
||
# Create, but don't save the new author instance.
|
||
>>> new_author = f.save(commit=False)
|
||
|
||
# Modify the author in some way.
|
||
>>> new_author.some_field = 'some_value'
|
||
|
||
# Save the new instance.
|
||
>>> new_author.save()
|
||
|
||
# Now, save the many-to-many data for the form.
|
||
>>> f.save_m2m()
|
||
|
||
Calling ``save_m2m()`` is only required if you use ``save(commit=False)``.
|
||
When you use a simple ``save()`` on a form, all data -- including
|
||
many-to-many data -- is saved without the need for any additional method calls.
|
||
For example:
|
||
|
||
.. code-block:: python
|
||
|
||
# Create a form instance with POST data.
|
||
>>> a = Author()
|
||
>>> f = AuthorForm(request.POST, instance=a)
|
||
|
||
# Create and save the new author instance. There's no need to do anything else.
|
||
>>> new_author = f.save()
|
||
|
||
Other than the ``save()`` and ``save_m2m()`` methods, a ``ModelForm`` works
|
||
exactly the same way as any other ``forms`` form. For example, the
|
||
``is_valid()`` method is used to check for validity, the ``is_multipart()``
|
||
method is used to determine whether a form requires multipart file upload (and
|
||
hence whether ``request.FILES`` must be passed to the form), etc. See
|
||
:ref:`binding-uploaded-files` for more information.
|
||
|
||
.. _modelforms-selecting-fields:
|
||
|
||
Selecting the fields to use
|
||
---------------------------
|
||
|
||
It is strongly recommended that you explicitly set all fields that should be
|
||
edited in the form using the ``fields`` attribute. Failure to do so can easily
|
||
lead to security problems when a form unexpectedly allows a user to set certain
|
||
fields, especially when new fields are added to a model. Depending on how the
|
||
form is rendered, the problem may not even be visible on the web page.
|
||
|
||
The alternative approach would be to include all fields automatically, or
|
||
blacklist only some. This fundamental approach is known to be much less secure
|
||
and has led to serious exploits on major websites (e.g. `GitHub
|
||
<https://github.com/blog/1068-public-key-security-vulnerability-and-mitigation>`_).
|
||
|
||
There are, however, two shortcuts available for cases where you can guarantee
|
||
these security concerns do not apply to you:
|
||
|
||
1. Set the ``fields`` attribute to the special value ``'__all__'`` to indicate
|
||
that all fields in the model should be used. For example::
|
||
|
||
from django.forms import ModelForm
|
||
|
||
class AuthorForm(ModelForm):
|
||
class Meta:
|
||
model = Author
|
||
fields = '__all__'
|
||
|
||
2. Set the ``exclude`` attribute of the ``ModelForm``’s inner ``Meta`` class to
|
||
a list of fields to be excluded from the form.
|
||
|
||
For example::
|
||
|
||
class PartialAuthorForm(ModelForm):
|
||
class Meta:
|
||
model = Author
|
||
exclude = ['title']
|
||
|
||
Since the ``Author`` model has the 3 fields ``name``, ``title`` and
|
||
``birth_date``, this will result in the fields ``name`` and ``birth_date``
|
||
being present on the form.
|
||
|
||
If either of these are used, the order the fields appear in the form will be the
|
||
order the fields are defined in the model, with ``ManyToManyField`` instances
|
||
appearing last.
|
||
|
||
In addition, Django applies the following rule: if you set ``editable=False`` on
|
||
the model field, *any* form created from the model via ``ModelForm`` will not
|
||
include that field.
|
||
|
||
.. versionchanged:: 1.6
|
||
|
||
Before version 1.6, the ``'__all__'`` shortcut did not exist, but omitting
|
||
the ``fields`` attribute had the same effect. Omitting both ``fields`` and
|
||
``exclude`` is now deprecated, but will continue to work as before until
|
||
version 1.8
|
||
|
||
|
||
.. note::
|
||
|
||
Any fields not included in a form by the above logic
|
||
will not be set by the form's ``save()`` method. Also, if you
|
||
manually add the excluded fields back to the form, they will not
|
||
be initialized from the model instance.
|
||
|
||
Django will prevent any attempt to save an incomplete model, so if
|
||
the model does not allow the missing fields to be empty, and does
|
||
not provide a default value for the missing fields, any attempt to
|
||
``save()`` a ``ModelForm`` with missing fields will fail. To
|
||
avoid this failure, you must instantiate your model with initial
|
||
values for the missing, but required fields::
|
||
|
||
author = Author(title='Mr')
|
||
form = PartialAuthorForm(request.POST, instance=author)
|
||
form.save()
|
||
|
||
Alternatively, you can use ``save(commit=False)`` and manually set
|
||
any extra required fields::
|
||
|
||
form = PartialAuthorForm(request.POST)
|
||
author = form.save(commit=False)
|
||
author.title = 'Mr'
|
||
author.save()
|
||
|
||
See the `section on saving forms`_ for more details on using
|
||
``save(commit=False)``.
|
||
|
||
.. _section on saving forms: `The save() method`_
|
||
|
||
.. _modelforms-overriding-default-fields:
|
||
|
||
Overriding the default fields
|
||
-----------------------------
|
||
|
||
The default field types, as described in the `Field types`_ table above, are
|
||
sensible defaults. If you have a ``DateField`` in your model, chances are you'd
|
||
want that to be represented as a ``DateField`` in your form. But
|
||
``ModelForm`` gives you the flexibility of changing the form field type and
|
||
widget for a given model field.
|
||
|
||
To specify a custom widget for a field, use the ``widgets`` attribute of the
|
||
inner ``Meta`` class. This should be a dictionary mapping field names to widget
|
||
classes or instances.
|
||
|
||
For example, if you want the a ``CharField`` for the ``name``
|
||
attribute of ``Author`` to be represented by a ``<textarea>`` instead
|
||
of its default ``<input type="text">``, you can override the field's
|
||
widget::
|
||
|
||
from django.forms import ModelForm, Textarea
|
||
from myapp.models import Author
|
||
|
||
class AuthorForm(ModelForm):
|
||
class Meta:
|
||
model = Author
|
||
fields = ('name', 'title', 'birth_date')
|
||
widgets = {
|
||
'name': Textarea(attrs={'cols': 80, 'rows': 20}),
|
||
}
|
||
|
||
The ``widgets`` dictionary accepts either widget instances (e.g.,
|
||
``Textarea(...)``) or classes (e.g., ``Textarea``).
|
||
|
||
.. versionadded:: 1.6
|
||
|
||
The ``labels``, ``help_texts`` and ``error_messages`` options were added.
|
||
|
||
Similarly, you can specify the ``labels``, ``help_texts`` and ``error_messages``
|
||
attributes of the inner ``Meta`` class if you want to further customize a field.
|
||
|
||
For example if you wanted to customize the wording of all user facing strings for
|
||
the ``name`` field::
|
||
|
||
class AuthorForm(ModelForm):
|
||
class Meta:
|
||
model = Author
|
||
fields = ('name', 'title', 'birth_date')
|
||
labels = {
|
||
'name': _('Writer'),
|
||
}
|
||
help_texts = {
|
||
'name': _('Some useful help text.'),
|
||
}
|
||
error_messages = {
|
||
'name': {
|
||
'max_length': _("This writer's name is too long."),
|
||
},
|
||
}
|
||
|
||
Finally, if you want complete control over of a field -- including its type,
|
||
validators, etc. -- you can do this by declaratively specifying fields like you
|
||
would in a regular ``Form``.
|
||
|
||
For example, if you wanted to use ``MySlugFormField`` for the ``slug``
|
||
field, you could do the following::
|
||
|
||
from django.forms import ModelForm
|
||
from myapp.models import Article
|
||
|
||
class ArticleForm(ModelForm):
|
||
slug = MySlugFormField()
|
||
|
||
class Meta:
|
||
model = Article
|
||
fields = ['pub_date', 'headline', 'content', 'reporter']
|
||
|
||
|
||
If you want to specify a field's validators, you can do so by defining
|
||
the field declaratively and setting its ``validators`` parameter::
|
||
|
||
from django.forms import ModelForm, DateField
|
||
from myapp.models import Article
|
||
|
||
class ArticleForm(ModelForm):
|
||
slug = CharField(validators=[validate_slug])
|
||
|
||
class Meta:
|
||
model = Article
|
||
fields = ['pub_date', 'headline', 'content', 'reporter', 'slug']
|
||
|
||
.. note::
|
||
|
||
When you explicitly instantiate a form field like this, it is important to
|
||
understand how ``ModelForm`` and regular ``Form`` are related.
|
||
|
||
``ModelForm`` is a regular ``Form`` which can automatically generate
|
||
certain fields. The fields that are automatically generated depend on
|
||
the content of the ``Meta`` class and on which fields have already been
|
||
defined declaratively. Basically, ``ModelForm`` will **only** generate fields
|
||
that are **missing** from the form, or in other words, fields that weren't
|
||
defined declaratively.
|
||
|
||
Fields defined declaratively are left as-is, therefore any customizations
|
||
made to ``Meta`` attributes such as ``widgets``, ``labels``, ``help_texts``,
|
||
or ``error_messages`` are ignored; these only apply to fields that are
|
||
generated automatically.
|
||
|
||
Similarly, fields defined declaratively do not draw their attributes like
|
||
``max_length`` or ``required`` from the corresponding model. If you want to
|
||
maintain the behavior specified in the model, you must set the relevant
|
||
arguments explicitly when declaring the form field.
|
||
|
||
For example, if the ``Article`` model looks like this::
|
||
|
||
class Article(models.Model):
|
||
headline = models.CharField(max_length=200, null=True, blank=True,
|
||
help_text="Use puns liberally")
|
||
content = models.TextField()
|
||
|
||
and you want to do some custom validation for ``headline``, while keeping
|
||
the ``blank`` and ``help_text`` values as specified, you might define
|
||
``ArticleForm`` like this::
|
||
|
||
class ArticleForm(ModelForm):
|
||
headline = MyFormField(max_length=200, required=False,
|
||
help_text="Use puns liberally")
|
||
|
||
class Meta:
|
||
model = Article
|
||
fields = ['headline', 'content']
|
||
|
||
You must ensure that the type of the form field can be used to set the
|
||
contents of the corresponding model field. When they are not compatible,
|
||
you will get a ``ValueError`` as no implicit conversion takes place.
|
||
|
||
See the :doc:`form field documentation </ref/forms/fields>` for more information
|
||
on fields and their arguments.
|
||
|
||
|
||
Enabling localization of fields
|
||
-------------------------------
|
||
|
||
.. versionadded:: 1.6
|
||
|
||
By default, the fields in a ``ModelForm`` will not localize their data. To
|
||
enable localization for fields, you can use the ``localized_fields``
|
||
attribute on the ``Meta`` class.
|
||
|
||
>>> from django.forms import ModelForm
|
||
>>> from myapp.models import Author
|
||
>>> class AuthorForm(ModelForm):
|
||
... class Meta:
|
||
... model = Author
|
||
... localized_fields = ('birth_date',)
|
||
|
||
If ``localized_fields`` is set to the special value ``'__all__'``, all fields
|
||
will be localized.
|
||
|
||
Form inheritance
|
||
----------------
|
||
|
||
As with basic forms, you can extend and reuse ``ModelForms`` by inheriting
|
||
them. This is useful if you need to declare extra fields or extra methods on a
|
||
parent class for use in a number of forms derived from models. For example,
|
||
using the previous ``ArticleForm`` class::
|
||
|
||
>>> class EnhancedArticleForm(ArticleForm):
|
||
... def clean_pub_date(self):
|
||
... ...
|
||
|
||
This creates a form that behaves identically to ``ArticleForm``, except there's
|
||
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 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.
|
||
|
||
* 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
|
||
``Meta`` of the first parent, etc.
|
||
|
||
.. versionchanged:: 1.7
|
||
|
||
* It's possible to inherit from both ``Form`` and ``ModelForm`` simultaneuosly,
|
||
however, you must ensure that ``ModelForm`` appears first in the MRO. This is
|
||
because these classes rely on different metaclasses and a class can only have
|
||
one metaclass.
|
||
|
||
.. versionadded:: 1.7
|
||
|
||
* It's possible to opt-out from a ``Field`` inherited from a parent class by
|
||
shadowing it. While any non-``Field`` value works for this purpose, it's
|
||
recommended to use ``None`` to make it explicit that a field is being
|
||
nullified.
|
||
|
||
You can only use this technique to opt out from a field defined declaratively
|
||
by a parent class; it won't prevent the ``ModelForm`` metaclass from generating
|
||
a default field. To opt-out from default fields, see
|
||
:ref:`controlling-fields-with-fields-and-exclude`.
|
||
|
||
.. _modelforms-factory:
|
||
|
||
ModelForm factory function
|
||
--------------------------
|
||
|
||
You can create forms from a given model using the standalone function
|
||
:func:`~django.forms.models.modelform_factory`, instead of using a class
|
||
definition. This may be more convenient if you do not have many customizations
|
||
to make::
|
||
|
||
>>> from django.forms.models import modelform_factory
|
||
>>> from myapp.models import Book
|
||
>>> BookForm = modelform_factory(Book, fields=("author", "title"))
|
||
|
||
This can also be used to make simple modifications to existing forms, for
|
||
example by specifying the widgets to be used for a given field::
|
||
|
||
>>> from django.forms import Textarea
|
||
>>> Form = modelform_factory(Book, form=BookForm,
|
||
... widgets={"title": Textarea()})
|
||
|
||
The fields to include can be specified using the ``fields`` and ``exclude``
|
||
keyword arguments, or the corresponding attributes on the ``ModelForm`` inner
|
||
``Meta`` class. Please see the ``ModelForm`` :ref:`modelforms-selecting-fields`
|
||
documentation.
|
||
|
||
... or enable localization for specific fields::
|
||
|
||
>>> Form = modelform_factory(Author, form=AuthorForm, localized_fields=("birth_date",))
|
||
|
||
.. _model-formsets:
|
||
|
||
Model formsets
|
||
==============
|
||
|
||
.. class:: models.BaseModelFormSet
|
||
|
||
Like :doc:`regular formsets </topics/forms/formsets>`, Django provides a couple
|
||
of enhanced formset classes that make it easy to work with Django models. Let's
|
||
reuse the ``Author`` model from above::
|
||
|
||
>>> from django.forms.models import modelformset_factory
|
||
>>> from myapp.models import Author
|
||
>>> AuthorFormSet = modelformset_factory(Author)
|
||
|
||
This will create a formset that is capable of working with the data associated
|
||
with the ``Author`` model. It works just like a regular formset::
|
||
|
||
>>> formset = AuthorFormSet()
|
||
>>> print(formset)
|
||
<input type="hidden" name="form-TOTAL_FORMS" value="1" id="id_form-TOTAL_FORMS" /><input type="hidden" name="form-INITIAL_FORMS" value="0" id="id_form-INITIAL_FORMS" /><input type="hidden" name="form-MAX_NUM_FORMS" id="id_form-MAX_NUM_FORMS" />
|
||
<tr><th><label for="id_form-0-name">Name:</label></th><td><input id="id_form-0-name" type="text" name="form-0-name" maxlength="100" /></td></tr>
|
||
<tr><th><label for="id_form-0-title">Title:</label></th><td><select name="form-0-title" id="id_form-0-title">
|
||
<option value="" selected="selected">---------</option>
|
||
<option value="MR">Mr.</option>
|
||
<option value="MRS">Mrs.</option>
|
||
<option value="MS">Ms.</option>
|
||
</select></td></tr>
|
||
<tr><th><label for="id_form-0-birth_date">Birth date:</label></th><td><input type="text" name="form-0-birth_date" id="id_form-0-birth_date" /><input type="hidden" name="form-0-id" id="id_form-0-id" /></td></tr>
|
||
|
||
.. note::
|
||
|
||
:func:`~django.forms.models.modelformset_factory` uses
|
||
:func:`~django.forms.formsets.formset_factory` to generate formsets. This
|
||
means that a model formset is just an extension of a basic formset that
|
||
knows how to interact with a particular model.
|
||
|
||
Changing the queryset
|
||
---------------------
|
||
|
||
By default, when you create a formset from a model, the formset will use a
|
||
queryset that includes all objects in the model (e.g.,
|
||
``Author.objects.all()``). You can override this behavior by using the
|
||
``queryset`` argument::
|
||
|
||
>>> formset = AuthorFormSet(queryset=Author.objects.filter(name__startswith='O'))
|
||
|
||
Alternatively, you can create a subclass that sets ``self.queryset`` in
|
||
``__init__``::
|
||
|
||
from django.forms.models import BaseModelFormSet
|
||
from myapp.models import Author
|
||
|
||
class BaseAuthorFormSet(BaseModelFormSet):
|
||
def __init__(self, *args, **kwargs):
|
||
super(BaseAuthorFormSet, self).__init__(*args, **kwargs)
|
||
self.queryset = Author.objects.filter(name__startswith='O')
|
||
|
||
Then, pass your ``BaseAuthorFormSet`` class to the factory function::
|
||
|
||
>>> AuthorFormSet = modelformset_factory(Author, formset=BaseAuthorFormSet)
|
||
|
||
If you want to return a formset that doesn't include *any* pre-existing
|
||
instances of the model, you can specify an empty QuerySet::
|
||
|
||
>>> AuthorFormSet(queryset=Author.objects.none())
|
||
|
||
|
||
.. _controlling-fields-with-fields-and-exclude:
|
||
|
||
Controlling which fields are used with ``fields`` and ``exclude``
|
||
-----------------------------------------------------------------
|
||
|
||
By default, a model formset uses all fields in the model that are not marked
|
||
with ``editable=False``. However, this can be overridden at the formset level::
|
||
|
||
>>> AuthorFormSet = modelformset_factory(Author, fields=('name', 'title'))
|
||
|
||
Using ``fields`` restricts the formset to use only the given fields.
|
||
Alternatively, you can take an "opt-out" approach, specifying which fields to
|
||
exclude::
|
||
|
||
>>> AuthorFormSet = modelformset_factory(Author, exclude=('birth_date',))
|
||
|
||
Specifying widgets to use in the form with ``widgets``
|
||
------------------------------------------------------
|
||
|
||
.. versionadded:: 1.6
|
||
|
||
Using the ``widgets`` parameter, you can specify a dictionary of values to
|
||
customize the ``ModelForm``’s widget class for a particular field. This
|
||
works the same way as the ``widgets`` dictionary on the inner ``Meta``
|
||
class of a ``ModelForm`` works::
|
||
|
||
>>> AuthorFormSet = modelformset_factory(
|
||
... Author, widgets={'name': Textarea(attrs={'cols': 80, 'rows': 20})
|
||
|
||
Enabling localization for fields with ``localized_fields``
|
||
----------------------------------------------------------
|
||
|
||
.. versionadded:: 1.6
|
||
|
||
Using the ``localized_fields`` parameter, you can enable localization for
|
||
fields in the form.
|
||
|
||
>>> AuthorFormSet = modelformset_factory(
|
||
... Author, localized_fields=('value',))
|
||
|
||
If ``localized_fields`` is set to the special value ``'__all__'``, all fields
|
||
will be localized.
|
||
|
||
Providing initial values
|
||
------------------------
|
||
|
||
As with regular formsets, it's possible to :ref:`specify initial data
|
||
<formsets-initial-data>` for forms in the formset by specifying an ``initial``
|
||
parameter when instantiating the model formset class returned by
|
||
:func:`~django.forms.models.modelformset_factory`. However, with model
|
||
formsets, the initial values only apply to extra forms, those that aren't bound
|
||
to an existing object instance.
|
||
|
||
.. _saving-objects-in-the-formset:
|
||
|
||
Saving objects in the formset
|
||
-----------------------------
|
||
|
||
As with a ``ModelForm``, you can save the data as a model object. This is done
|
||
with the formset's ``save()`` method::
|
||
|
||
# Create a formset instance with POST data.
|
||
>>> formset = AuthorFormSet(request.POST)
|
||
|
||
# Assuming all is valid, save the data.
|
||
>>> instances = formset.save()
|
||
|
||
The ``save()`` method returns the instances that have been saved to the
|
||
database. If a given instance's data didn't change in the bound data, the
|
||
instance won't be saved to the database and won't be included in the return
|
||
value (``instances``, in the above example).
|
||
|
||
When fields are missing from the form (for example because they have been
|
||
excluded), these fields will not be set by the ``save()`` method. You can find
|
||
more information about this restriction, which also holds for regular
|
||
``ModelForms``, in `Selecting the fields to use`_.
|
||
|
||
Pass ``commit=False`` to return the unsaved model instances::
|
||
|
||
# don't save to the database
|
||
>>> instances = formset.save(commit=False)
|
||
>>> for instance in instances:
|
||
... # do something with instance
|
||
... instance.save()
|
||
|
||
This gives you the ability to attach data to the instances before saving them
|
||
to the database. If your formset contains a ``ManyToManyField``, you'll also
|
||
need to call ``formset.save_m2m()`` to ensure the many-to-many relationships
|
||
are saved properly.
|
||
|
||
After calling ``save()``, your model formset will have three new attributes
|
||
containing the formset's changes:
|
||
|
||
.. attribute:: models.BaseModelFormSet.changed_objects
|
||
.. attribute:: models.BaseModelFormSet.deleted_objects
|
||
.. attribute:: models.BaseModelFormSet.new_objects
|
||
|
||
.. _model-formsets-max-num:
|
||
|
||
Limiting the number of editable objects
|
||
---------------------------------------
|
||
|
||
As with regular formsets, you can use the ``max_num`` and ``extra`` parameters
|
||
to :func:`~django.forms.models.modelformset_factory` to limit the number of
|
||
extra forms displayed.
|
||
|
||
``max_num`` does not prevent existing objects from being displayed::
|
||
|
||
>>> Author.objects.order_by('name')
|
||
[<Author: Charles Baudelaire>, <Author: Paul Verlaine>, <Author: Walt Whitman>]
|
||
|
||
>>> AuthorFormSet = modelformset_factory(Author, max_num=1)
|
||
>>> formset = AuthorFormSet(queryset=Author.objects.order_by('name'))
|
||
>>> [x.name for x in formset.get_queryset()]
|
||
[u'Charles Baudelaire', u'Paul Verlaine', u'Walt Whitman']
|
||
|
||
If the value of ``max_num`` is greater than the number of existing related
|
||
objects, up to ``extra`` additional blank forms will be added to the formset,
|
||
so long as the total number of forms does not exceed ``max_num``::
|
||
|
||
>>> AuthorFormSet = modelformset_factory(Author, max_num=4, extra=2)
|
||
>>> formset = AuthorFormSet(queryset=Author.objects.order_by('name'))
|
||
>>> for form in formset:
|
||
... print(form.as_table())
|
||
<tr><th><label for="id_form-0-name">Name:</label></th><td><input id="id_form-0-name" type="text" name="form-0-name" value="Charles Baudelaire" maxlength="100" /><input type="hidden" name="form-0-id" value="1" id="id_form-0-id" /></td></tr>
|
||
<tr><th><label for="id_form-1-name">Name:</label></th><td><input id="id_form-1-name" type="text" name="form-1-name" value="Paul Verlaine" maxlength="100" /><input type="hidden" name="form-1-id" value="3" id="id_form-1-id" /></td></tr>
|
||
<tr><th><label for="id_form-2-name">Name:</label></th><td><input id="id_form-2-name" type="text" name="form-2-name" value="Walt Whitman" maxlength="100" /><input type="hidden" name="form-2-id" value="2" id="id_form-2-id" /></td></tr>
|
||
<tr><th><label for="id_form-3-name">Name:</label></th><td><input id="id_form-3-name" type="text" name="form-3-name" maxlength="100" /><input type="hidden" name="form-3-id" id="id_form-3-id" /></td></tr>
|
||
|
||
A ``max_num`` value of ``None`` (the default) puts a high limit on the number
|
||
of forms displayed (1000). In practice this is equivalent to no limit.
|
||
|
||
Using a model formset in a view
|
||
-------------------------------
|
||
|
||
Model formsets are very similar to formsets. Let's say we want to present a
|
||
formset to edit ``Author`` model instances::
|
||
|
||
from django.forms.models import modelformset_factory
|
||
from django.shortcuts import render_to_response
|
||
from myapp.models import Author
|
||
|
||
def manage_authors(request):
|
||
AuthorFormSet = modelformset_factory(Author)
|
||
if request.method == 'POST':
|
||
formset = AuthorFormSet(request.POST, request.FILES)
|
||
if formset.is_valid():
|
||
formset.save()
|
||
# do something.
|
||
else:
|
||
formset = AuthorFormSet()
|
||
return render_to_response("manage_authors.html", {
|
||
"formset": formset,
|
||
})
|
||
|
||
As you can see, the view logic of a model formset isn't drastically different
|
||
than that of a "normal" formset. The only difference is that we call
|
||
``formset.save()`` to save the data into the database. (This was described
|
||
above, in :ref:`saving-objects-in-the-formset`.)
|
||
|
||
.. _model-formsets-overriding-clean:
|
||
|
||
Overriding ``clean()`` on a ``ModelFormSet``
|
||
--------------------------------------------
|
||
|
||
Just like with ``ModelForms``, by default the ``clean()`` method of a
|
||
``ModelFormSet`` will validate that none of the items in the formset violate
|
||
the unique constraints on your model (either ``unique``, ``unique_together`` or
|
||
``unique_for_date|month|year``). If you want to override the ``clean()`` method
|
||
on a ``ModelFormSet`` and maintain this validation, you must call the parent
|
||
class's ``clean`` method::
|
||
|
||
from django.forms.models import BaseModelFormSet
|
||
|
||
class MyModelFormSet(BaseModelFormSet):
|
||
def clean(self):
|
||
super(MyModelFormSet, self).clean()
|
||
# example custom validation across forms in the formset
|
||
for form in self.forms:
|
||
# your custom formset validation
|
||
...
|
||
|
||
Using a custom queryset
|
||
-----------------------
|
||
|
||
As stated earlier, you can override the default queryset used by the model
|
||
formset::
|
||
|
||
from django.forms.models import modelformset_factory
|
||
from django.shortcuts import render_to_response
|
||
from myapp.models import Author
|
||
|
||
def manage_authors(request):
|
||
AuthorFormSet = modelformset_factory(Author)
|
||
if request.method == "POST":
|
||
formset = AuthorFormSet(request.POST, request.FILES,
|
||
queryset=Author.objects.filter(name__startswith='O'))
|
||
if formset.is_valid():
|
||
formset.save()
|
||
# Do something.
|
||
else:
|
||
formset = AuthorFormSet(queryset=Author.objects.filter(name__startswith='O'))
|
||
return render_to_response("manage_authors.html", {
|
||
"formset": formset,
|
||
})
|
||
|
||
Note that we pass the ``queryset`` argument in both the ``POST`` and ``GET``
|
||
cases in this example.
|
||
|
||
Using the formset in the template
|
||
---------------------------------
|
||
|
||
.. highlight:: html+django
|
||
|
||
There are three ways to render a formset in a Django template.
|
||
|
||
First, you can let the formset do most of the work::
|
||
|
||
<form method="post" action="">
|
||
{{ formset }}
|
||
</form>
|
||
|
||
Second, you can manually render the formset, but let the form deal with
|
||
itself::
|
||
|
||
<form method="post" action="">
|
||
{{ formset.management_form }}
|
||
{% for form in formset %}
|
||
{{ form }}
|
||
{% endfor %}
|
||
</form>
|
||
|
||
When you manually render the forms yourself, be sure to render the management
|
||
form as shown above. See the :ref:`management form documentation
|
||
<understanding-the-managementform>`.
|
||
|
||
Third, you can manually render each field::
|
||
|
||
<form method="post" action="">
|
||
{{ formset.management_form }}
|
||
{% for form in formset %}
|
||
{% for field in form %}
|
||
{{ field.label_tag }} {{ field }}
|
||
{% endfor %}
|
||
{% endfor %}
|
||
</form>
|
||
|
||
If you opt to use this third method and you don't iterate over the fields with
|
||
a ``{% for %}`` loop, you'll need to render the primary key field. For example,
|
||
if you were rendering the ``name`` and ``age`` fields of a model::
|
||
|
||
<form method="post" action="">
|
||
{{ formset.management_form }}
|
||
{% for form in formset %}
|
||
{{ form.id }}
|
||
<ul>
|
||
<li>{{ form.name }}</li>
|
||
<li>{{ form.age }}</li>
|
||
</ul>
|
||
{% endfor %}
|
||
</form>
|
||
|
||
Notice how we need to explicitly render ``{{ form.id }}``. This ensures that
|
||
the model formset, in the ``POST`` case, will work correctly. (This example
|
||
assumes a primary key named ``id``. If you've explicitly defined your own
|
||
primary key that isn't called ``id``, make sure it gets rendered.)
|
||
|
||
.. highlight:: python
|
||
|
||
.. _inline-formsets:
|
||
|
||
Inline formsets
|
||
===============
|
||
|
||
.. class:: models.BaseInlineFormSet
|
||
|
||
Inline formsets is a small abstraction layer on top of model formsets. These
|
||
simplify the case of working with related objects via a foreign key. Suppose
|
||
you have these two models::
|
||
|
||
from django.db import models
|
||
|
||
class Author(models.Model):
|
||
name = models.CharField(max_length=100)
|
||
|
||
class Book(models.Model):
|
||
author = models.ForeignKey(Author)
|
||
title = models.CharField(max_length=100)
|
||
|
||
If you want to create a formset that allows you to edit books belonging to
|
||
a particular author, you could do this::
|
||
|
||
>>> from django.forms.models import inlineformset_factory
|
||
>>> BookFormSet = inlineformset_factory(Author, Book)
|
||
>>> author = Author.objects.get(name=u'Mike Royko')
|
||
>>> formset = BookFormSet(instance=author)
|
||
|
||
.. note::
|
||
|
||
:func:`~django.forms.models.inlineformset_factory` uses
|
||
:func:`~django.forms.models.modelformset_factory` and marks
|
||
``can_delete=True``.
|
||
|
||
.. seealso::
|
||
|
||
:ref:`Manually rendered can_delete and can_order <manually-rendered-can-delete-and-can-order>`.
|
||
|
||
Overriding methods on an ``InlineFormSet``
|
||
------------------------------------------
|
||
|
||
When overriding methods on ``InlineFormSet``, you should subclass
|
||
:class:`~models.BaseInlineFormSet` rather than
|
||
:class:`~models.BaseModelFormSet`.
|
||
|
||
For example, if you want to override ``clean()``::
|
||
|
||
from django.forms.models import BaseInlineFormSet
|
||
|
||
class CustomInlineFormSet(BaseInlineFormSet):
|
||
def clean(self):
|
||
super(CustomInlineFormSet, self).clean()
|
||
# example custom validation across forms in the formset
|
||
for form in self.forms:
|
||
# your custom formset validation
|
||
...
|
||
|
||
See also :ref:`model-formsets-overriding-clean`.
|
||
|
||
Then when you create your inline formset, pass in the optional argument
|
||
``formset``::
|
||
|
||
>>> from django.forms.models import inlineformset_factory
|
||
>>> BookFormSet = inlineformset_factory(Author, Book, formset=CustomInlineFormSet)
|
||
>>> author = Author.objects.get(name=u'Mike Royko')
|
||
>>> formset = BookFormSet(instance=author)
|
||
|
||
More than one foreign key to the same model
|
||
-------------------------------------------
|
||
|
||
If your model contains more than one foreign key to the same model, you'll
|
||
need to resolve the ambiguity manually using ``fk_name``. For example, consider
|
||
the following model::
|
||
|
||
class Friendship(models.Model):
|
||
from_friend = models.ForeignKey(Friend)
|
||
to_friend = models.ForeignKey(Friend)
|
||
length_in_months = models.IntegerField()
|
||
|
||
To resolve this, you can use ``fk_name`` to
|
||
:func:`~django.forms.models.inlineformset_factory`::
|
||
|
||
>>> FriendshipFormSet = inlineformset_factory(Friend, Friendship, fk_name="from_friend")
|
||
|
||
Using an inline formset in a view
|
||
---------------------------------
|
||
|
||
You may want to provide a view that allows a user to edit the related objects
|
||
of a model. Here's how you can do that::
|
||
|
||
def manage_books(request, author_id):
|
||
author = Author.objects.get(pk=author_id)
|
||
BookInlineFormSet = inlineformset_factory(Author, Book)
|
||
if request.method == "POST":
|
||
formset = BookInlineFormSet(request.POST, request.FILES, instance=author)
|
||
if formset.is_valid():
|
||
formset.save()
|
||
# Do something. Should generally end with a redirect. For example:
|
||
return HttpResponseRedirect(author.get_absolute_url())
|
||
else:
|
||
formset = BookInlineFormSet(instance=author)
|
||
return render_to_response("manage_books.html", {
|
||
"formset": formset,
|
||
})
|
||
|
||
Notice how we pass ``instance`` in both the ``POST`` and ``GET`` cases.
|
||
|
||
Specifying widgets to use in the inline form
|
||
--------------------------------------------
|
||
|
||
.. versionadded:: 1.6
|
||
|
||
``inlineformset_factory`` uses ``modelformset_factory`` and passes most
|
||
of its arguments to ``modelformset_factory``. This means you can use
|
||
the ``widgets`` parameter in much the same way as passing it to
|
||
``modelformset_factory``. See `Specifying widgets to use in the form with widgets`_ above.
|