- 1.5
- Documentation version: development
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:
# 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:
# 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(ContactView, self).form_valid(form) Notes:
- FormView inherits TemplateResponseMixin so template_name can be used here.
- The default implementation for form_valid() simply redirects to the success_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:
# models.py 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:
# views.py 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.
In Django 1.6, the fields attribute was added, which works the same way as the fields attribute on the inner Meta class on ModelForm.
Omitting the fields attribute will work as previously, but is deprecated and this attribute will be required from 1.8 (unless you define the form class in another way).
Finally, we hook these new views into the URLconf:
# urls.py from django.conf.urls import patterns, url from myapp.views import AuthorCreate, AuthorUpdate, AuthorDelete urlpatterns = patterns('', # ... url(r'author/add/$', AuthorCreate.as_view(), name='author_add'), url(r'author/(?P<pk>\d+)/$', AuthorUpdate.as_view(), name='author_update'), url(r'author/(?P<pk>\d+)/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 and UpdateView use myapp/author_form.html
- DeleteView uses myapp/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:
# models.py from django.contrib.auth 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:
# 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(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:
import json from django.http import HttpResponse 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 render_to_json_response(self, context, **response_kwargs): data = json.dumps(context) response_kwargs['content_type'] = 'application/json' return HttpResponse(data, **response_kwargs) def form_invalid(self, form): response = super(AjaxableResponseMixin, self).form_invalid(form) if self.request.is_ajax(): return self.render_to_json_response(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 self.render_to_json_response(data) else: return response class AuthorCreate(AjaxableResponseMixin, CreateView): model = Author fields = ['name'] Questions/Feedback
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