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			582 lines
		
	
	
		
			24 KiB
		
	
	
	
		
			Plaintext
		
	
	
	
	
	
| .. _topics-forms-modelforms:
 | |
| 
 | |
| ==========================
 | |
| Creating forms from models
 | |
| ==========================
 | |
| 
 | |
| ``ModelForm``
 | |
| =============
 | |
| 
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| If you're building a database-driven app, chances are you'll have forms that
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| map closely to Django models. For instance, you might have a ``BlogComment``
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| model, and you want to create a form that lets people submit comments. In this
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| case, it would be redundant to define the field types in your form, because
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| you've already defined the fields in your model.
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| 
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| For this reason, Django provides a helper class that let you create a ``Form``
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| class from a Django model.
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| 
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| For example::
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| 
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|     >>> from django.forms import ModelForm
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| 
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|     # Create the form class.
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|     >>> class ArticleForm(ModelForm):
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|     ...     class Meta:
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|     ...         model = Article
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| 
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|     # Creating a form to add an article.
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|     >>> form = ArticleForm()
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| 
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|     # Creating a form to change an existing article.
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|     >>> article = Article.objects.get(pk=1)
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|     >>> form = ArticleForm(instance=article)
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| 
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| Field types
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| -----------
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| 
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| The generated ``Form`` class will have a form field for every model field. Each
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| model field has a corresponding default form field. For example, a
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| ``CharField`` on a model is represented as a ``CharField`` on a form. A
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| model ``ManyToManyField`` is represented as a ``MultipleChoiceField``. Here is
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| the full list of conversions:
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| 
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|     ===============================  ========================================
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|     Model field                      Form field
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|     ===============================  ========================================
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|     ``AutoField``                    Not represented in the form
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|     ``BooleanField``                 ``BooleanField``
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|     ``CharField``                    ``CharField`` with ``max_length`` set to
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|                                      the model field's ``max_length``
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|     ``CommaSeparatedIntegerField``   ``CharField``
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|     ``DateField``                    ``DateField``
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|     ``DateTimeField``                ``DateTimeField``
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|     ``DecimalField``                 ``DecimalField``
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|     ``EmailField``                   ``EmailField``
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|     ``FileField``                    ``FileField``
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|     ``FilePathField``                ``CharField``
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|     ``FloatField``                   ``FloatField``
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|     ``ForeignKey``                   ``ModelChoiceField`` (see below)
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|     ``ImageField``                   ``ImageField``
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|     ``IntegerField``                 ``IntegerField``
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|     ``IPAddressField``               ``IPAddressField``
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|     ``ManyToManyField``              ``ModelMultipleChoiceField`` (see
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|                                      below)
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|     ``NullBooleanField``             ``CharField``
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|     ``PhoneNumberField``             ``USPhoneNumberField``
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|                                      (from ``django.contrib.localflavor.us``)
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|     ``PositiveIntegerField``         ``IntegerField``
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|     ``PositiveSmallIntegerField``    ``IntegerField``
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|     ``SlugField``                    ``SlugField``
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|     ``SmallIntegerField``            ``IntegerField``
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|     ``TextField``                    ``CharField`` with ``widget=Textarea``
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|     ``TimeField``                    ``TimeField``
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|     ``URLField``                     ``URLField`` with ``verify_exists`` set
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|                                      to the model field's ``verify_exists``
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|     ``XMLField``                     ``CharField`` with ``widget=Textarea``
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|     ===============================  ========================================
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| 
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| 
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| .. note::
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|     The ``FloatField`` form field and ``DecimalField`` model and form fields
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|     are new in the development version.
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| 
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| As you might expect, the ``ForeignKey`` and ``ManyToManyField`` model field
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| types are special cases:
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| 
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|     * ``ForeignKey`` is represented by ``django.forms.ModelChoiceField``,
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|       which is a ``ChoiceField`` whose choices are a model ``QuerySet``.
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| 
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|     * ``ManyToManyField`` is represented by
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|       ``django.forms.ModelMultipleChoiceField``, which is a
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|       ``MultipleChoiceField`` whose choices are a model ``QuerySet``.
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| 
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| In addition, each generated form field has attributes set as follows:
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| 
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|     * If the model field has ``blank=True``, then ``required`` is set to
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|       ``False`` on the form field. Otherwise, ``required=True``.
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| 
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|     * The form field's ``label`` is set to the ``verbose_name`` of the model
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|       field, with the first character capitalized.
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| 
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|     * The form field's ``help_text`` is set to the ``help_text`` of the model
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|       field.
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| 
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|     * If the model field has ``choices`` set, then the form field's ``widget``
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|       will be set to ``Select``, with choices coming from the model field's
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|       ``choices``. The choices will normally include the blank choice which is
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|       selected by default. If the field is required, this forces the user to
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|       make a selection. The blank choice will not be included if the model
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|       field has ``blank=False`` and an explicit ``default`` value (the
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|       ``default`` value will be initially selected instead).
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| 
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| Finally, note that you can override the form field used for a given model
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| field. See `Overriding the default field types`_ below.
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| 
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| A full example
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| --------------
 | |
| 
 | |
| Consider this set of models::
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| 
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|     from django.db import models
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|     from django.forms import ModelForm
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| 
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|     TITLE_CHOICES = (
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|         ('MR', 'Mr.'),
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|         ('MRS', 'Mrs.'),
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|         ('MS', 'Ms.'),
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|     )
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| 
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|     class Author(models.Model):
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|         name = models.CharField(max_length=100)
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|         title = models.CharField(max_length=3, choices=TITLE_CHOICES)
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|         birth_date = models.DateField(blank=True, null=True)
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| 
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|         def __unicode__(self):
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|             return self.name
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| 
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|     class Book(models.Model):
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|         name = models.CharField(max_length=100)
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|         authors = models.ManyToManyField(Author)
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| 
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|     class AuthorForm(ModelForm):
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|         class Meta:
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|             model = Author
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| 
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|     class BookForm(ModelForm):
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|         class Meta:
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|             model = Book
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| 
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| With these models, the ``ModelForm`` subclasses above would be roughly
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| equivalent to this (the only difference being the ``save()`` method, which
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| we'll discuss in a moment.)::
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| 
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|     class AuthorForm(forms.Form):
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|         name = forms.CharField(max_length=100)
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|         title = forms.CharField(max_length=3,
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|                     widget=forms.Select(choices=TITLE_CHOICES))
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|         birth_date = forms.DateField(required=False)
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| 
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|     class BookForm(forms.Form):
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|         name = forms.CharField(max_length=100)
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|         authors = forms.ModelMultipleChoiceField(queryset=Author.objects.all())
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| 
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| The ``save()`` method
 | |
| ---------------------
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| 
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| Every form produced by ``ModelForm`` also has a ``save()``
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| method. This method creates and saves a database object from the data
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| bound to the form. A subclass of ``ModelForm`` can accept an existing
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| model instance as the keyword argument ``instance``; if this is
 | |
| supplied, ``save()`` will update that instance. If it's not supplied,
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| ``save()`` will create a new instance of the specified model::
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| 
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|     # Create a form instance from POST data.
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|     >>> f = ArticleForm(request.POST)
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| 
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|     # Save a new Article object from the form's data.
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|     >>> new_article = f.save()
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| 
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|     # Create a form to edit an existing Article.
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|     >>> a = Article.objects.get(pk=1)
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|     >>> f = ArticleForm(instance=a)
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|     >>> f.save()
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| 
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|     # Create a form to edit an existing Article, but use
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|     # POST data to populate the form.
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|     >>> a = Article.objects.get(pk=1)
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|     >>> f = ArticleForm(request.POST, instance=a)
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|     >>> f.save()
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| 
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| Note that ``save()`` will raise a ``ValueError`` if the data in the form
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| doesn't validate -- i.e., ``if form.errors``.
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| 
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| This ``save()`` method accepts an optional ``commit`` keyword argument, which
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| accepts either ``True`` or ``False``. If you call ``save()`` with
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| ``commit=False``, then it will return an object that hasn't yet been saved to
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| the database. In this case, it's up to you to call ``save()`` on the resulting
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| model instance. This is useful if you want to do custom processing on the
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| object before saving it. ``commit`` is ``True`` by default.
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| 
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| Another side effect of using ``commit=False`` is seen when your model has
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| a many-to-many relation with another model. If your model has a many-to-many
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| relation and you specify ``commit=False`` when you save a form, Django cannot
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| immediately save the form data for the many-to-many relation. This is because
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| it isn't possible to save many-to-many data for an instance until the instance
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| exists in the database.
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| 
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| To work around this problem, every time you save a form using ``commit=False``,
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| Django adds a ``save_m2m()`` method to your ``ModelForm`` subclass. After
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| you've manually saved the instance produced by the form, you can invoke
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| ``save_m2m()`` to save the many-to-many form data. For example::
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| 
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|     # Create a form instance with POST data.
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|     >>> f = AuthorForm(request.POST)
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| 
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|     # Create, but don't save the new author instance.
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|     >>> new_author = f.save(commit=False)
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| 
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|     # Modify the author in some way.
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|     >>> new_author.some_field = 'some_value'
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| 
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|     # Save the new instance.
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|     >>> new_author.save()
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| 
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|     # Now, save the many-to-many data for the form.
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|     >>> f.save_m2m()
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| 
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| Calling ``save_m2m()`` is only required if you use ``save(commit=False)``.
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| When you use a simple ``save()`` on a form, all data -- including
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| many-to-many data -- is saved without the need for any additional method calls.
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| For example::
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| 
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|     # Create a form instance with POST data.
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|     >>> a = Author()
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|     >>> f = AuthorForm(request.POST, instance=a)
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| 
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|     # Create and save the new author instance. There's no need to do anything else.
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|     >>> new_author = f.save()
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| 
 | |
| Other than the ``save()`` and ``save_m2m()`` methods, a ``ModelForm`` works
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| exactly the same way as any other ``forms`` form. For example, the
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| ``is_valid()`` method is used to check for validity, the ``is_multipart()``
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| method is used to determine whether a form requires multipart file upload (and
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| hence whether ``request.FILES`` must be passed to the form), etc. See
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| :ref:`topics-forms-index` for more information.
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| 
 | |
| Using a subset of fields on the form
 | |
| ------------------------------------
 | |
| 
 | |
| In some cases, you may not want all the model fields to appear on the generated
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| form. There are three ways of telling ``ModelForm`` to use only a subset of the
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| model fields:
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| 
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| 1. Set ``editable=False`` on the model field. As a result, *any* form
 | |
|    created from the model via ``ModelForm`` will not include that
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|    field.
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| 
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| 2. Use the ``fields`` attribute of the ``ModelForm``'s inner ``Meta``
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|    class.  This attribute, if given, should be a list of field names
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|    to include in the form.
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| 
 | |
| 3. Use the ``exclude`` attribute of the ``ModelForm``'s inner ``Meta``
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|    class.  This attribute, if given, should be a list of field names
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|    to exclude from the form.
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| 
 | |
| For example, if you want a form for the ``Author`` model (defined
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| above) that includes only the ``name`` and ``title`` fields, you would
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| specify ``fields`` or ``exclude`` like this::
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| 
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|     class PartialAuthorForm(ModelForm):
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|         class Meta:
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|             model = Author
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|             fields = ('name', 'title')
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|     
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|     class PartialAuthorForm(ModelForm):
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|         class Meta:
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|             model = Author
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|             exclude = ('birth_date',)
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| 
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| Since the Author model has only 3 fields, 'name', 'title', and
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| 'birth_date', the forms above will contain exactly the same fields.
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| 
 | |
| .. note::
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| 
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|     If you specify ``fields`` or ``exclude`` when creating a form with
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|     ``ModelForm``, then the fields that are not in the resulting form will not
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|     be set by the form's ``save()`` method. Django will prevent any attempt to
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|     save an incomplete model, so if the model does not allow the missing fields
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|     to be empty, and does not provide a default value for the missing fields,
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|     any attempt to ``save()`` a ``ModelForm`` with missing fields will fail.
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|     To avoid this failure, you must instantiate your model with initial values
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|     for the missing, but required fields, or use ``save(commit=False)`` and
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|     manually set any extra required fields::
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| 
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|         instance = Instance(required_field='value')
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|         form = InstanceForm(request.POST, instance=instance)
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|         new_instance = form.save()
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| 
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|         instance = form.save(commit=False)
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|         instance.required_field = 'new value'
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|         new_instance = instance.save()
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| 
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|     See the `section on saving forms`_ for more details on using
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|     ``save(commit=False)``.
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| 
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| .. _section on saving forms: `The save() method`_
 | |
| 
 | |
| Overriding the default field types
 | |
| ----------------------------------
 | |
| 
 | |
| 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
 | |
| for a given model field. You do this by declaratively specifying fields like
 | |
| you would in a regular ``Form``. Declared fields will override the default
 | |
| ones generated by using the ``model`` attribute.
 | |
| 
 | |
| For example, if you wanted to use ``MyDateFormField`` for the ``pub_date``
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| field, you could do the following::
 | |
| 
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|     >>> class ArticleForm(ModelForm):
 | |
|     ...     pub_date = MyDateFormField()
 | |
|     ...
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|     ...     class Meta:
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|     ...         model = Article
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| 
 | |
| If you want to override a field's default widget, then specify the ``widget``
 | |
| parameter when declaring the form field::
 | |
| 
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|    >>> class ArticleForm(ModelForm):
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|    ...     pub_date = DateField(widget=MyDateWidget())
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|    ...
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|    ...     class Meta:
 | |
|    ...         model = Article
 | |
| 
 | |
| Overriding the clean() method
 | |
| -----------------------------
 | |
| 
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| You can override the ``clean()`` method on a model form to provide additional
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| validation in the same way you can on a normal form. However, by default the
 | |
| ``clean()`` method validates the uniqueness of fields that are marked as unique
 | |
| or unique_together on the model. Therefore, if you would like to override
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| the ``clean()`` method and maintain the default validation, you must call the
 | |
| parent class's ``clean()`` method.
 | |
| 
 | |
| 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
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| parent class for use in a number of forms derived from models. For example,
 | |
| using the previous ``ArticleForm`` class::
 | |
| 
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|     >>> class EnhancedArticleForm(ArticleForm):
 | |
|     ...     def clean_pub_date(self):
 | |
|     ...         ...
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| 
 | |
| 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::
 | |
| 
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|     >>> class RestrictedArticleForm(EnhancedArticleForm):
 | |
|     ...     class Meta(ArticleForm.Meta):
 | |
|     ...         exclude = ['body']
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| 
 | |
| 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.
 | |
| 
 | |
|  * For technical reasons, a subclass cannot inherit from both a ``ModelForm``
 | |
|    and a ``Form`` simultaneously.
 | |
| 
 | |
| Chances are these notes won't affect you unless you're trying to do something
 | |
| tricky with subclassing.
 | |
| 
 | |
| .. _model-formsets:
 | |
| 
 | |
| Model Formsets
 | |
| ==============
 | |
| 
 | |
| Similar to :ref:`regular formsets <topics-forms-formsets>` there are a couple
 | |
| enhanced formset classes that provide all the right things to work with your
 | |
| models. Lets reuse the ``Author`` model from above::
 | |
| 
 | |
|     >>> from django.forms.models import modelformset_factory
 | |
|     >>> AuthorFormSet = modelformset_factory(Author)
 | |
| 
 | |
| This will create a formset that is capable of working with the data associated
 | |
| to the ``Author`` model. It works just like a regular formset just that we are
 | |
| working with ``ModelForm`` instances instead of ``Form`` instances::
 | |
| 
 | |
|     >>> 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" />
 | |
|     <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::
 | |
|     ``modelformset_factory`` uses ``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 queryset will be all
 | |
| objects in the model. This is best shown as ``Author.objects.all()``. This is
 | |
| configurable::
 | |
| 
 | |
|     >>> formset = AuthorFormSet(queryset=Author.objects.filter(name__startswith='O'))
 | |
| 
 | |
| Alternatively, you can use a subclassing based approach::
 | |
| 
 | |
|     from django.forms.models import BaseModelFormSet
 | |
|     
 | |
|     class BaseAuthorFormSet(BaseModelFormSet):
 | |
|         def get_queryset(self):
 | |
|             return super(BaseAuthorFormSet, self).get_queryset().filter(name__startswith='O')
 | |
| 
 | |
| Then your ``BaseAuthorFormSet`` would be passed into the factory function to
 | |
| be used as a base::
 | |
| 
 | |
|     >>> AuthorFormSet = modelformset_factory(Author, formset=BaseAuthorFormSet)
 | |
| 
 | |
| Controlling which fields are used with ``fields`` and ``exclude``
 | |
| -----------------------------------------------------------------
 | |
| 
 | |
| By default a model formset will use all fields in the model that are not marked
 | |
| with ``editable=False``. However, this can be overidden at the formset level::
 | |
| 
 | |
|     >>> AuthorFormSet = modelformset_factory(Author, fields=('name', 'title'))
 | |
| 
 | |
| Using ``fields`` will restrict the formset to use just the given fields. Or if
 | |
| you need to go the other way::
 | |
| 
 | |
|     >>> AuthorFormSet = modelformset_factory(Author, exclude=('birth_date',))
 | |
| 
 | |
| Using ``exclude`` will prevent the given fields from being used in the formset.
 | |
| 
 | |
| .. _saving-objects-in-the-formset:
 | |
| 
 | |
| Saving objects in the formset
 | |
| -----------------------------
 | |
| 
 | |
| Similar to a ``ModelForm`` you can save the data into the model. This is done
 | |
| with the ``save()`` method on the formset::
 | |
| 
 | |
|     # create a formset instance with POST data.
 | |
|     >>> formset = AuthorFormSet(request.POST)
 | |
|     
 | |
|     # assuming all is valid, save the data
 | |
|     >>> instances = formset.save()
 | |
| 
 | |
| The ``save()`` method will return the instances that have been saved to the
 | |
| database. If an instance did not change in the bound data it will not be
 | |
| saved to the database and not found in ``instances`` in the above example.
 | |
| 
 | |
| You can optionally pass in ``commit=False`` to ``save()`` to only return the
 | |
| model instances without any database interaction::
 | |
| 
 | |
|     # 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 will also
 | |
| need to make a call to ``formset.save_m2m()`` to ensure the many-to-many
 | |
| relationships are saved properly.
 | |
| 
 | |
| .. _model-formsets-max-num:
 | |
| 
 | |
| Limiting the number of objects editable
 | |
| ---------------------------------------
 | |
| 
 | |
| Similar to regular formsets you can use the ``max_num`` parameter to
 | |
| ``modelformset_factory`` to limit the number of forms displayed. With
 | |
| model formsets this will properly limit the query to only select the maximum
 | |
| number of objects needed::
 | |
| 
 | |
|     >>> Author.objects.order_by('name')
 | |
|     [<Author: Charles Baudelaire>, <Author: Paul Verlaine>, <Author: Walt Whitman>]
 | |
|     
 | |
|     >>> AuthorFormSet = modelformset_factory(Author, max_num=2, extra=1)
 | |
|     >>> formset = AuthorFormSet(queryset=Author.objects.order_by('name'))
 | |
|     >>> formset.initial
 | |
|     [{'id': 1, 'name': u'Charles Baudelaire'}, {'id': 3, 'name': u'Paul Verlaine'}]
 | |
| 
 | |
| If the value of ``max_num`` is less than the total objects returned it will
 | |
| fill the rest with extra forms::
 | |
| 
 | |
|     >>> AuthorFormSet = modelformset_factory(Author, max_num=4, extra=1)
 | |
|     >>> formset = AuthorFormSet(queryset=Author.objects.order_by('name'))
 | |
|     >>> for form in formset.forms:
 | |
|     ...     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>
 | |
| 
 | |
| Using a model formset in a view
 | |
| -------------------------------
 | |
| 
 | |
| Model formsets are very similar to formsets. Lets say we want to present a
 | |
| formset to a user to edit ``Author`` model instances::
 | |
| 
 | |
|     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()
 | |
|         render_to_response("manage_authors.html", {
 | |
|             "formset": formset,
 | |
|         })
 | |
| 
 | |
| As you can see the view is not drastically different than how to use a formset
 | |
| in a view. The only difference is that we call ``formset.save()`` to save the
 | |
| data into the database. This is described above in
 | |
| :ref:`saving-objects-in-the-formset`.
 | |
| 
 | |
| Using ``inlineformset_factory``
 | |
| -------------------------------
 | |
| 
 | |
| The ``inlineformset_factory`` is a helper to a common usage pattern of working
 | |
| with related objects through a foreign key. It takes all the same options as
 | |
| a ``modelformset_factory``. Suppose you have these two 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
 | |
| some author you would do::
 | |
| 
 | |
|     >>> from django.forms.models import inlineformset_factory
 | |
|     >>> BookFormSet = inlineformset_factory(Author, Book)
 | |
|     >>> author = Author.objects.get(name=u'Orson Scott Card')
 | |
|     >>> formset = BookFormSet(instance=author)
 | |
| 
 | |
| .. note::
 | |
|     ``inlineformset_factory`` uses ``modelformset_factory`` and marks
 | |
|     ``can_delete=True``.
 | |
| 
 | |
| More than one foreign key to the same model
 | |
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 | |
| 
 | |
| If your model contains more than one foreign key to the same model you will
 | |
| need to resolve the ambiguity manually using ``fk_name``. Given 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 simply use ``fk_name`` to ``inlineformset_factory``::
 | |
| 
 | |
|     >>> FrienshipFormSet = inlineformset_factory(Friend, Friendship, fk_name="from_friend")
 |