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django/docs/topics/class-based-views/generic-editing.txt
Sjoerd Job Postmus df41b5a05d Fixed #28593 -- Added a simplified URL routing syntax per DEP 0201.
Thanks Aymeric Augustin for shepherding the DEP and patch review.
Thanks Marten Kenbeek and Tim Graham for contributing to the code.
Thanks Tom Christie, Shai Berger, and Tim Graham for the docs.
2017-09-20 18:04:42 -04:00

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====================================
Form handling with class-based views
====================================
Form processing generally has 3 paths:
* Initial GET (blank or prepopulated form)
* POST with invalid data (typically redisplay form with errors)
* POST with valid data (process the data and typically redirect)
Implementing this yourself often results in a lot of repeated boilerplate code
(see :ref:`Using a form in a view<using-a-form-in-a-view>`). To help avoid
this, Django provides a collection of generic class-based views for form
processing.
Basic forms
===========
Given a simple contact form:
.. snippet::
:filename: forms.py
from django import forms
class ContactForm(forms.Form):
name = forms.CharField()
message = forms.CharField(widget=forms.Textarea)
def send_email(self):
# send email using the self.cleaned_data dictionary
pass
The view can be constructed using a ``FormView``:
.. snippet::
:filename: views.py
from myapp.forms import ContactForm
from django.views.generic.edit import FormView
class ContactView(FormView):
template_name = 'contact.html'
form_class = ContactForm
success_url = '/thanks/'
def form_valid(self, form):
# This method is called when valid form data has been POSTed.
# It should return an HttpResponse.
form.send_email()
return super().form_valid(form)
Notes:
* FormView inherits
:class:`~django.views.generic.base.TemplateResponseMixin` so
:attr:`~django.views.generic.base.TemplateResponseMixin.template_name`
can be used here.
* The default implementation for
:meth:`~django.views.generic.edit.FormMixin.form_valid` simply
redirects to the :attr:`~django.views.generic.edit.FormMixin.success_url`.
Model forms
===========
Generic views really shine when working with models. These generic
views will automatically create a :class:`~django.forms.ModelForm`, so long as
they can work out which model class to use:
* If the :attr:`~django.views.generic.edit.ModelFormMixin.model` attribute is
given, that model class will be used.
* If :meth:`~django.views.generic.detail.SingleObjectMixin.get_object()`
returns an object, the class of that object will be used.
* If a :attr:`~django.views.generic.detail.SingleObjectMixin.queryset` is
given, the model for that queryset will be used.
Model form views provide a
:meth:`~django.views.generic.edit.ModelFormMixin.form_valid()` implementation
that saves the model automatically. You can override this if you have any
special requirements; see below for examples.
You don't even need to provide a ``success_url`` for
:class:`~django.views.generic.edit.CreateView` or
:class:`~django.views.generic.edit.UpdateView` - they will use
:meth:`~django.db.models.Model.get_absolute_url()` on the model object if available.
If you want to use a custom :class:`~django.forms.ModelForm` (for instance to
add extra validation) simply set
:attr:`~django.views.generic.edit.FormMixin.form_class` on your view.
.. note::
When specifying a custom form class, you must still specify the model,
even though the :attr:`~django.views.generic.edit.FormMixin.form_class` may
be a :class:`~django.forms.ModelForm`.
First we need to add :meth:`~django.db.models.Model.get_absolute_url()` to our
``Author`` class:
.. snippet::
:filename: models.py
from django.urls import reverse
from django.db import models
class Author(models.Model):
name = models.CharField(max_length=200)
def get_absolute_url(self):
return reverse('author-detail', kwargs={'pk': self.pk})
Then we can use :class:`CreateView` and friends to do the actual
work. Notice how we're just configuring the generic class-based views
here; we don't have to write any logic ourselves:
.. snippet::
:filename: views.py
from django.views.generic.edit import CreateView, UpdateView, DeleteView
from django.urls import reverse_lazy
from myapp.models import Author
class AuthorCreate(CreateView):
model = Author
fields = ['name']
class AuthorUpdate(UpdateView):
model = Author
fields = ['name']
class AuthorDelete(DeleteView):
model = Author
success_url = reverse_lazy('author-list')
.. note::
We have to use :func:`~django.urls.reverse_lazy` here, not just
``reverse()`` as the urls are not loaded when the file is imported.
The ``fields`` attribute works the same way as the ``fields`` attribute on the
inner ``Meta`` class on :class:`~django.forms.ModelForm`. Unless you define the
form class in another way, the attribute is required and the view will raise
an :exc:`~django.core.exceptions.ImproperlyConfigured` exception if it's not.
If you specify both the :attr:`~django.views.generic.edit.ModelFormMixin.fields`
and :attr:`~django.views.generic.edit.FormMixin.form_class` attributes, an
:exc:`~django.core.exceptions.ImproperlyConfigured` exception will be raised.
Finally, we hook these new views into the URLconf:
.. snippet::
:filename: urls.py
from django.urls import path
from myapp.views import AuthorCreate, AuthorUpdate, AuthorDelete
urlpatterns = [
# ...
path('author/add/', AuthorCreate.as_view(), name='author-add'),
path('author/<int:pk>/', AuthorUpdate.as_view(), name='author-update'),
path('author/<int:pk>/delete/', AuthorDelete.as_view(), name='author-delete'),
]
.. note::
These views inherit
:class:`~django.views.generic.detail.SingleObjectTemplateResponseMixin`
which uses
:attr:`~django.views.generic.detail.SingleObjectTemplateResponseMixin.template_name_suffix`
to construct the
:attr:`~django.views.generic.base.TemplateResponseMixin.template_name`
based on the model.
In this example:
* :class:`CreateView` and :class:`UpdateView` use ``myapp/author_form.html``
* :class:`DeleteView` uses ``myapp/author_confirm_delete.html``
If you wish to have separate templates for :class:`CreateView` and
:class:`UpdateView`, you can set either
:attr:`~django.views.generic.base.TemplateResponseMixin.template_name` or
:attr:`~django.views.generic.detail.SingleObjectTemplateResponseMixin.template_name_suffix`
on your view class.
Models and ``request.user``
===========================
To track the user that created an object using a :class:`CreateView`,
you can use a custom :class:`~django.forms.ModelForm` to do this. First, add
the foreign key relation to the model:
.. snippet::
:filename: models.py
from django.contrib.auth.models import User
from django.db import models
class Author(models.Model):
name = models.CharField(max_length=200)
created_by = models.ForeignKey(User, on_delete=models.CASCADE)
# ...
In the view, ensure that you don't include ``created_by`` in the list of fields
to edit, and override
:meth:`~django.views.generic.edit.ModelFormMixin.form_valid()` to add the user:
.. snippet::
:filename: views.py
from django.views.generic.edit import CreateView
from myapp.models import Author
class AuthorCreate(CreateView):
model = Author
fields = ['name']
def form_valid(self, form):
form.instance.created_by = self.request.user
return super().form_valid(form)
Note that you'll need to :ref:`decorate this
view<decorating-class-based-views>` using
:func:`~django.contrib.auth.decorators.login_required`, or
alternatively handle unauthorized users in the
:meth:`~django.views.generic.edit.ModelFormMixin.form_valid()`.
AJAX example
============
Here is a simple example showing how you might go about implementing a form that
works for AJAX requests as well as 'normal' form POSTs::
from django.http import JsonResponse
from django.views.generic.edit import CreateView
from myapp.models import Author
class AjaxableResponseMixin:
"""
Mixin to add AJAX support to a form.
Must be used with an object-based FormView (e.g. CreateView)
"""
def form_invalid(self, form):
response = super().form_invalid(form)
if self.request.is_ajax():
return JsonResponse(form.errors, status=400)
else:
return response
def form_valid(self, form):
# We make sure to call the parent's form_valid() method because
# it might do some processing (in the case of CreateView, it will
# call form.save() for example).
response = super().form_valid(form)
if self.request.is_ajax():
data = {
'pk': self.object.pk,
}
return JsonResponse(data)
else:
return response
class AuthorCreate(AjaxableResponseMixin, CreateView):
model = Author
fields = ['name']