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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 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:
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
:
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(ContactView, self).form_valid(form)
Notes:
- FormView inherits
TemplateResponseMixin
sotemplate_name
can be used here. - The default implementation for
form_valid()
simply redirects to thesuccess_url
.
Model Forms¶
Generic views really shine when working with models. These generic
views will automatically create a ModelForm
, so long as
they can work out which model class to use:
- If the
model
attribute is given, that model class will be used. - If
get_object()
returns an object, the class of that object will be used. - If a
queryset
is given, the model for that queryset will be used.
Model form views provide a
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
CreateView
or
UpdateView
- they will use
get_absolute_url()
on the model object if available.
If you want to use a custom ModelForm
(for instance to
add extra validation) simply set
form_class
on your view.
Note
When specifying a custom form class, you must still specify the model,
even though the form_class
may
be a ModelForm
.
First we need to add get_absolute_url()
to our
Author
class:
from django.core.urlresolvers 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 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:
from django.views.generic.edit import CreateView, UpdateView, DeleteView
from django.core.urlresolvers 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 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 ModelForm
. Unless you define the
form class in another way, the attribute is required and the view will raise
an ImproperlyConfigured
exception if it’s not.
If you specify both the fields
and form_class
attributes, an
ImproperlyConfigured
exception will be raised.
Omitting the fields
attribute was previously allowed and resulted in a
form with all of the model’s fields.
Previously if both fields
and form_class
were specified,
fields
was silently ignored.
Finally, we hook these new views into the URLconf:
from django.conf.urls import url
from myapp.views import AuthorCreate, AuthorUpdate, AuthorDelete
urlpatterns = [
# ...
url(r'author/add/$', AuthorCreate.as_view(), name='author-add'),
url(r'author/(?P<pk>[0-9]+)/$', AuthorUpdate.as_view(), name='author-update'),
url(r'author/(?P<pk>[0-9]+)/delete/$', AuthorDelete.as_view(), name='author-delete'),
]
Note
These views inherit
SingleObjectTemplateResponseMixin
which uses
template_name_suffix
to construct the
template_name
based on the model.
In this example:
CreateView
andUpdateView
usemyapp/author_form.html
DeleteView
usesmyapp/author_confirm_delete.html
If you wish to have separate templates for CreateView
and
UpdateView
, you can set either
template_name
or
template_name_suffix
on your view class.
Models and request.user¶
To track the user that created an object using a CreateView
,
you can use a custom ModelForm
to do this. First, add
the foreign key relation to the model:
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)
# ...
In the view, ensure that you don’t include created_by
in the list of fields
to edit, and override
form_valid()
to add the user:
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(AuthorCreate, self).form_valid(form)
Note that you’ll need to decorate this
view using
login_required()
, or
alternatively handle unauthorized users in the
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(object):
"""
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(AjaxableResponseMixin, self).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(AjaxableResponseMixin, self).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']