Is there an easy way to call an existing ViewSet retrieve call from another viewset?

[David Kaplan]

I would like to call an existing ViewSet that I have created from a new ViewSet. The existing viewset I want to call handles all of my User data updates and retrievals. The new viewset takes a userid as a parameter in order to look up related objects. I would like to reuse the existing viewset because it already encapsulates my permission logic, filter logic, and custom retrieval logic for users and I want to use this same validation as a first step for this new call. I have been researching, but have not seen a solution posted.

The 2 problems I see is that viewset functions like retrieve take in a Request and return a Response. I could create and manually pack a request and manually unpack a response within my new viewset, but I feel icky just writing that.

Is there an easier more standard way to reuse viewsets as internal APIs?

[Filipe Ximenes]

Hi David, pardon if I din't understand the question but wouldn't creating a mixin to be shared by the 2 ViewSets solve this? This way you would have a separate class with the code that can be used by the ViewSets and extend it in each one of then.

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[David Kaplan]

Hi Filipe,
I don't think that would work if I am understanding the suggestion.
Let me try to clarify:

I have a userprofile modelviewset that looks something like this:

class UserProfileViewSet(viewsets.ModelViewSet):
    permission_classes =(CustomPermissionClass, )
    queryset = UserProfile.objects.all()
    serializer_class = UserProfileSerializer

class ProjectViewSet(viewset.ModelViewSet):
    permission_classes = (AnotherCustomPermissionClass,)
    queryset =Project.objects.all()
    serializer_class = ProjectSerializer

    @list_route(methods=['get'])
    def forprofile(request, *args, **kwargs):
        user_id = request.query_params.get('user_id', None)

        #This is where I would like to be able to use the retrieve functionality that django rest framework provides for free to lookup the user and save it to a "user" variable

        projects = self.get_queryset().filter(user=user)
        serializer = self.get_serializer(projects, many=True)
        return Response(serializer.data)

So if you look at the above. I would like to be able to use the existing retrieve function that is automatically defined on the UserProfileViewSet so that I can take advantage of django rest framework and the permissions I have defined for that class.
I can create a mixin for the UserProfileViewSet that can define the permission_classes, serializer_class and queryset. That mixin would work for other UserProfileViewsets, but would not work for a viewset for a completely different asset (like project), because those assets also need their own definition of queryset and permission_classes.
Let me know if I misunderstood.

On Tuesday, June 30, 2015 at 12:30:11 PM UTC-4, Filipe Ximenes wrote:

Hi David, pardon if I din't understand the question but wouldn't creating a mixin to be shared by the 2 ViewSets solve this? This way you would have a separate class with the code that can be used by the ViewSets and extend it in each one of then.

On Mon, Jun 29, 2015 at 10:12 PM, David Kaplan <dave.b...@gmail.com> wrote:

I would like to call an existing ViewSet that I have created from a new ViewSet. The existing viewset I want to call handles all of my User data updates and retrievals. The new viewset takes a userid as a parameter in order to look up related objects. I would like to reuse the existing viewset because it already encapsulates my permission logic, filter logic, and custom retrieval logic for users and I want to use this same validation as a first step for this new call. I have been researching, but have not seen a solution posted.

The 2 problems I see is that viewset functions like retrieve take in a Request and return a Response. I could create and manually pack a request and manually unpack a response within my new viewset, but I feel icky just writing that.

Is there an easier more standard way to reuse viewsets as internal APIs?

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[Filipe Ximenes]

Yep, you are right.

Again, not sure I got 100%, but see if this works:

I didn't test it so I may have forgotten something but I hope you can get the idea. Also, not the most beautiful solution.

from rest_framework import permissions

class CustomViewPermission(permissions.BasePermission):

    def has_permission(self, request, view):
        if hasattr(view, 'custom_permission'):
            return view.custom_permission(request)
        return True

    def has_object_permission(self, request, view, obj):
        if hasattr(view, 'custom_object_permission'):
            return view.custom_object_permission(request, obj)
        return True

class UserProcessMixin(object):

    def custom_object_permission(request, obj):
        # do your permission checking here
        # using self.user NOT obj
        return True # or False depending on your checking

class UserProfileViewSet(UserProcessMixin, viewsets.ModelViewSet):
    permission_classes =(CustomViewPermission, )
    queryset = UserProfile.objects.all()
    serializer_class = UserProfileSerializer

    def get_object(self):
        self.user = super(UserProfileViewSet, self).get_object()
        return self.user

class ProjectViewSet(UserProcessMixin, viewset.ModelViewSet):
    permission_classes = (CustomViewPermission,)
    queryset =Project.objects.all()
    serializer_class = ProjectSerializer

    def get_user(self, user_id):
        self.user = User.objects.get(id=user_id)
        return self.user

    @list_route(methods=['get'])
    def forprofile(request, *args, **kwargs):
        user_id = request.query_params.get('user_id', None)

        self.get_user(user_id)
        self.check_object_permissions(self.request, None)

        projects = self.get_queryset().filter(user=user)
        serializer = self.get_serializer(projects, many=True)
        return Response(serializer.data)

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[David Kaplan]

Thanks for the help Filipe. This is what I expected. I was hoping to be able to reuse the view so that I don't have to duplicate its logic in other apis, but it does not look like that is an option. I will have to do something like what you suggested where I access the model directly. The reason I was hoping to use the UserViewSet is so that if I make a change there it will apply to everything that uses it.

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[Rocky Meza]

I've always liked the idea of calling my API from within Python, for reasons of DRYness and dogfooding.

I was able to do it like this:

def another_view(request, *args, **kwargs):
    viewfn = MyViewSet.as_view({'get': 'retrieve'})
    response = viewfn(request, *args, **kwargs)
    # directly use response.data

It's been a while since I wrote it, but I think you get the idea.

Eventually I was hoping to have a requests-like library that could be used for calling the API, then if I ever had to separate the app server from the API server, I could just switch to requests.