Django Rest Framework: Retrieving object count from a model - json

Question

Does anyone know how can I successfully retrieve the object count of a model, in JSON format, and how I need to configure my routing? I'm trying to achieve this using a APIView and returning a Response formatted by JSONRenderer.
UPDATE:
#api_view(['GET'])
#renderer_classes((JSONRenderer, JSONPRenderer))
def InfluenciasCountView(request, format=None):
influencia_count = Influencia.objects.count()
content = {'influencia_count': influencia_count}
return Response(content)
Here's the route I'm using:
url(r'^influencias/count/$', views.InfluenciasCountView, name='influencias-count')

Answer 1

Check out this snippet of code (the second one). If this does not suit your need, please add some of your code (for better understanding).
UPDATE
For routing, DRF offers a default router for each view. This means that you can have the following configuration in your urls.py: (using the example from the previous link)
url(r'^users/count/$', views. UserCountView.as_view(), name='users-count')
Then, when you access the URL your_base_url/users/count/ you will see something like {'user_count': 10}.
UPDATE 2
The entire code should look like this:
class UserCountView(APIView):
"""
A view that returns the count of active users.
"""
renderer_classes = (JSONRenderer, )
def get(self, request, format=None):
user_count = User.objects.count()
content = {'user_count': user_count}
return Response(content)

Answer 2

I am using routers from REST Framework to build my URLs. I tried above code but doesn't get it working. One of the problems is I cannot get /count/ into the router endpoints.
I checked DRF document (3.8.2) and found that there is a (new?) #action decorator (I was using 3.7.7 and it doesn't have it). So, here is my full solutions:
Upgrade DRF to 3.8.2 (or above) in requirements.txt (or PipFile if you using that).
Add a new action count method to the ModelViewSet
Update get_permissions to include the newly added action count
Here is my views.py:
from rest_framework.decorators import action
from rest_framework.response import Response
class PostViewSet(viewsets.ModelViewSet):
"""
API endpoint that allows recommend to be viewed or edited.
"""
model = Post
queryset = Post.objects.filter(is_active=True)
serializer_class = serializers.PostSerializer
filter_backends = (filters.SearchFilter, DjangoFilterBackend,)
search_fields = ('title', 'body',)
filter_fields = ('status', 'type')
def get_permissions(self):
if self.action in ('list', 'retrieve', 'create', 'count'):
return (AllowAny()),
if self.action in ('update', 'partial_update'):
return (IsAdminUser()),
return (IsAdminUser()),
#action(detail=False)
def count(self, request):
queryset = self.filter_queryset(self.get_queryset())
count = queryset.count()
content = {'count': count}
return Response(content)
To query count of posts: /api/posts/count/?format=json
To query count of published: /api/posts/count/?format=json&status=published
One of the important thing here is to use the queryset from filter_queryset(...), rather than Post.objects.all().
UPDATE
Since count is common, I created a mixin for that.
from rest_framework.decorators import action
from rest_framework.response import Response
class CountModelMixin(object):
"""
Count a queryset.
"""
#action(detail=False)
def count(self, request, *args, **kwargs):
queryset = self.filter_queryset(self.get_queryset())
content = {'count': queryset.count()}
return Response(content)
To use it, just add CountModelMixin to your ModelViewSet (also support nested ModelViewSet).
class PostViewSet(viewsets.ModelViewSet, CountModelMixin):
If you use permissions, also add 'count' to the list of granted action.