use get_object_or_404() method with mongoengine

Question

I'm starting to learn Django using Mongodb, creating a poll app following the djangoproject tutorial. I have a problem at the moment of raising a 404 error. If I do this:

def detail(request, poll_id):
 try:
    poll = Poll.objects.get(pk=poll_id)
 except Poll.DoesNotExist:
    raise Http404
 return render(request, 'polls/detail.html', {'poll': poll})

it works, but if I try to use a django shortcut:

def detail(request, poll_id):
  poll = get_object_or_404(Poll, pk=poll_id)
  return render(request, 'polls/detail.html', {'poll': poll})

I get this error

Object is of type 'Poll', but must be a Django Model, Manager, or QuerySet

I think this error occurs because in models.py I've defined the Poll model as a mongoengine Document and not as a django Model

class Poll(Document):

What should I do to have the get_object_or_404() method working?

Answer 1

It's time to roll your own shortcut then?

def get_obj_or_404(klass, *args, **kwargs):
    try:
        return klass.objects.get(*args, **kwargs)
    except klass.DoesNotExist:
        raise Http404

def detail(request, poll_id):
    poll = get_obj_or_404(Poll, pk=poll_id)
    return render(request, 'polls/detail.html', {'poll': poll})

I haven't tested it yet but that's the basic idea.

I don't think you are doing anything wrong, it's just that that Django shortcut doesn't support the Document class. Check the Django source code, specifically the function get_object_or_404() (which uses the function _get_queryset(), the one that raised the exception you got) then I think you will understand.