How to cache a view method without a route? - django

Question

I'm trying to test caching in my code. I am using memcached as the backend. I set the CACHE config to use memcached under 'basic'. There isn't a direct route to the get_stuff method. Here is my code:
I have a view that looks like
from .models import MyModel
from django.views.decorators.cache import cache_page
class MyView(TemplateView):
""" Django view ... """
template_name = "home.html"
#cache_page(60 * 15, cache="basic")
def get_stuff(self): # pylint: disable=no-self-use
""" Get all ... """
return MyModel.objects.filter(visible=True, type=MyModel.CONSTANT)
def get_context_data(self, **kwargs):
context = super(MyView, self).get_context_data(**kwargs)
stuffs = self.get_stuff()
if stuffs:
context['stuff'] = random.choice(stuffs)
return context
I also have a test that looks like
from django.test.client import RequestFactory
from xyz.apps.appname import views
class MyViewTestCase(TestCase):
""" Unit tests for the MyView class """
def test_caching_get_stuff(self):
""" Tests that we are properly caching the query to get all stuffs """
view = views.MyView.as_view()
factory = RequestFactory()
request = factory.get('/')
response = view(request)
print response.context_data['stuff']
When I run my test I get this error:
Traceback (most recent call last):
File "/path/to/app/appname/tests.py", line 142, in test_caching_get_stuff
response = view(request)
File "/usr/local/lib/python2.7/site-packages/django/views/generic/base.py", line 69, in view
return self.dispatch(request, *args, **kwargs)
File "/usr/local/lib/python2.7/site-packages/django/views/generic/base.py", line 87, in dispatch
return handler(request, *args, **kwargs)
File "/usr/local/lib/python2.7/site-packages/django/views/generic/base.py", line 154, in get
context = self.get_context_data(**kwargs)
File "/path/to/app/appname/views.py", line 50, in get_context_data
stuffs = self.get_stuff()
File "/usr/local/lib/python2.7/site-packages/django/utils/decorators.py", line 91, in _wrapped_view
result = middleware.process_request(request)
File "/usr/local/lib/python2.7/site-packages/django/middleware/cache.py", line 134, in process_request
if not request.method in ('GET', 'HEAD'):
AttributeError: 'MyView' object has no attribute 'method'
What is causing this and how do I fix this? I'm fairly new to Python and Django.

Answer 1

Can you show the what you have for MIDDLEWARE_CLASSES in settings.py? I looked through the code where your error showed up, and it notes that FetchFromCacheMiddleware must be last piece of middleware in the MIDDLEWARE_CLASSES. I wonder if that is causing your problem.
Related documentation here.

Answer 2

I believe the issue is that the cache_page decorator is meant to be used on view functions, not to decorate methods of class-based views. View functions take 'request' as their first argument, and if you look at the traceback, you can see that in fact the error is caused because the first argument of the function you tried to decorate is not a request but rather 'self' (i.e., the MyView object referred to in the error).
I am not sure if or how the cache_page decorator can be used for class-based views, though this page in the docs suggests a way of using it in the URLconf and I imagine you could wrap the return of ViewClass.as_view in a similar fashion. If the thing you're trying to wrap in caching is not properly a view but rather a utility function of some sort, you should drop to using the more manual lower-level cache API inside of your function (not as a decorator).