Use login_required with vary_on_headers with generic view in Django

Question

I'm have a generic view where I use the login_required decorator in the urls.py file, like this:

(r'^my-url/$', login_required(ListView.as_view())),

Now, I would like to use the vary_on_headers decorator for this url, but I can't get it working.

I've tried:

(r'^my-url/$', vary_on_headers(login_required(ListView.as_view()),'HTTP_X_REQUESTED_WITH'))

but I got the following error during my tests:

response = self.client.get('/my-url/', HTTP_X_REQUESTED_WITH='XMLHttpRequest')
  File "/lib/python2.6/site-packages/django/test/client.py", line 439, in get
    response = super(Client, self).get(path, data=data, **extra)
  File "/lib/python2.6/site-packages/django/test/client.py", line 241, in get
    return self.request(**r)
  File "/lib/python2.6/site-packages/django/core/handlers/base.py", line 178, in get_response
    response = middleware_method(request, response)
  File "/lib/python2.6/site-packages/django/middleware/common.py", line 94, in process_response
    if response.status_code == 404:
AttributeError: 'function' object has no attribute 'status_code'

If I try:

(r'^my-url/$', login_required(vary_on_headers(MyProductsView.as_view(),'HTTP_X_REQUESTED_WITH'))),

but I get the following error now:

response = self.client.get('/my-url/', HTTP_X_REQUESTED_WITH='XMLHttpRequest')
  File "/lib/python2.6/site-packages/django/test/client.py", line 439, in get
    response = super(Client, self).get(path, data=data, **extra)
  File "/lib/python2.6/site-packages/django/test/client.py", line 241, in get
    return self.request(**r)
  File "/lib/python2.6/site-packages/django/core/handlers/base.py", line 178, in get_response
    response = middleware_method(request, response)
  File "/lib/python2.6/site-packages/django/contrib/sessions/middleware.py", line 26, in process_response
    patch_vary_headers(response, ('Cookie',))
  File "/lib/python2.6/site-packages/django/utils/cache.py", line 133, in patch_vary_headers
    if response.has_header('Vary'):
AttributeError: 'function' object has no attribute 'has_header'

Any ideas on what could be happening and how to solve this problem?

Answer 1

You have mixed up the view function that you are decorating with the header arguments for the vary_on_headers decorator.

Try the following:

(r'^my-url/$', vary_on_headers('X_REQUESTED_WITH')(login_required(ListView.as_view())),

Or, if you want to apply the decorators the other way around:

(r'^my-url/$', login_required(vary_on_headers('X_REQUESTED_WITH')(ListView.as_view())),

Answer 2

If you have a custom view class (or base class), instead of decorating every call to as_view(), you can use method_decorator to decorate the get method of your view, or even dispatch:

from django.utils.decorators import method_decorator

@method_decorator(vary_on_headers('X-Requested-With'))
@method_decorator(login_required)
def dispatch(self, *args, **kwargs):
    return super(MyView, self).dispatch(*args, **kwargs)

You could also create a mixin that does that.