A view is a callable which takes a request and returns a response. This can be more than just a function, and Django provides an example of some classes which can be used as views. These allow you to structure your views and reuse code by harnessing inheritance and mixins. There are also some generic views for simple tasks which we’ll get to later, but you may want to design your own structure of reusable views which suits your use case. For full details, see the class-based views reference documentation.
Django provides base view classes which will suit a wide range of applications.
All views inherit from the
View class, which
handles linking the view in to the URLs, HTTP method dispatching and other
RedirectView is for a
simple HTTP redirect, and
extends the base class to make it also render a template.
Simple usage in your URLconf¶
The simplest way to use generic views is to create them directly in your
URLconf. If you’re only changing a few simple attributes on a class-based view,
you can simply pass them into the
as_view() method call itself:
from django.conf.urls import patterns from django.views.generic import TemplateView urlpatterns = patterns('', (r'^about/', TemplateView.as_view(template_name="about.html")), )
Any arguments passed to
override attributes set on the class. In this example, we set
TemplateView. A similar overriding pattern can be used for the
url attribute on
Subclassing generic views¶
The second, more powerful way to use generic views is to inherit from an
existing view and override attributes (such as the
methods (such as
get_context_data) in your subclass to provide new values
or methods. Consider, for example, a view that just displays one template,
about.html. Django has a generic view to do this -
TemplateView - so we can just subclass it,
and override the template name:
# some_app/views.py from django.views.generic import TemplateView class AboutView(TemplateView): template_name = "about.html"
Then we just need to add this new view into our URLconf.
~django.views.generic.base.TemplateView is a class, not a function, so we
point the URL to the
method instead, which provides a function-like entry to class-based views:
# urls.py from django.conf.urls import patterns from some_app.views import AboutView urlpatterns = patterns('', (r'^about/', AboutView.as_view()), )
For more information on how to use the built in generic views, consult the next topic on generic class based views.
Supporting other HTTP methods¶
Suppose somebody wants to access our book library over HTTP using the views as an API. The API client would connect every now and then and download book data for the books published since last visit. But if no new books appeared since then, it is a waste of CPU time and bandwidth to fetch the books from the database, render a full response and send it to the client. It might be preferable to ask the API when the most recent book was published.
We map the URL to book list view in the URLconf:
from django.conf.urls import patterns from books.views import BookListView urlpatterns = patterns('', (r'^books/$', BookListView.as_view()), )
And the view:
from django.http import HttpResponse from django.views.generic import ListView from books.models import Book class BookListView(ListView): model = Book def head(self, *args, **kwargs): last_book = self.get_queryset().latest('publication_date') response = HttpResponse('') # RFC 1123 date format response['Last-Modified'] = last_book.publication_date.strftime('%a, %d %b %Y %H:%M:%S GMT') return response
If the view is accessed from a
GET request, a plain-and-simple object
list is returned in the response (using
book_list.html template). But if
the client issues a
HEAD request, the response has an empty body and
Last-Modified header indicates when the most recent book was published.
Based on this information, the client may or may not download the full object
Decorating class-based views¶
Since class-based views aren’t functions, decorating them works differently
depending on if you’re using
as_view or creating a subclass.
Decorating in URLconf¶
The simplest way of decorating class-based views is to decorate the
result of the
The easiest place to do this is in the URLconf where you deploy your view:
from django.contrib.auth.decorators import login_required, permission_required from django.views.generic import TemplateView from .views import VoteView urlpatterns = patterns('', (r'^about/', login_required(TemplateView.as_view(template_name="secret.html"))), (r'^vote/', permission_required('polls.can_vote')(VoteView.as_view())), )
This approach applies the decorator on a per-instance basis. If you want every instance of a view to be decorated, you need to take a different approach.
Decorating the class¶
To decorate every instance of a class-based view, you need to decorate
the class definition itself. To do this you apply the decorator to the
dispatch() method of the class.
A method on a class isn’t quite the same as a standalone function, so
you can’t just apply a function decorator to the method – you need to
transform it into a method decorator first. The
decorator transforms a function decorator into a method decorator so
that it can be used on an instance method. For example:
from django.contrib.auth.decorators import login_required from django.utils.decorators import method_decorator from django.views.generic import TemplateView class ProtectedView(TemplateView): template_name = 'secret.html' @method_decorator(login_required) def dispatch(self, *args, **kwargs): return super(ProtectedView, self).dispatch(*args, **kwargs)
In this example, every instance of
ProtectedView will have
as parameters to the decorated method on the class. If your method
does not accept a compatible set of parameters it will raise a