Django - AttributeError: 'NoneType' object has no attribute 'method'

Question

I noticed that when I use DRF documentation I get error AttributeError: 'NoneType' object has no attribute 'method' and this is associated with this line if self.request.method == 'POST' Any ideas how can I solve it?

views.py:

@permission_classes([UserPermission])
class UserObject(GenericAPIView):

    def get_serializer_class(self):

        if self.request.method == 'POST':
            return ObjectPostSerializer
        return ObjectSerializer

    def post(self, request, user_id):

        serializer = ObjectSerializer(data=request.data)
        if serializer.is_valid():
            serializer.save(user_id=user_id)
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

    def get(self, request, user_id):

        try:
            object = Object.objects.filter(user=user_id)
        except Object.DoesNotExist:
            return Response(status=status.HTTP_404_NOT_FOUND)
        serializer = ObjectSerializer(object, many=True)
        return Response(serializer.data)

    def put(self, request, user_id):

        try:
            object = Object.objects.get(user=user_id)
        except Object.DoesNotExist:
            return Response(status=status.HTTP_404_NOT_FOUND)
        serializer = ObjectSerializer(object, data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

    def delete(self, request, user_id):

        try:
            object = Object.objects.filter(user=user_id)
        except Object.DoesNotExist:
            return Response(status=status.HTTP_404_NOT_FOUND)
        object.delete()
        return Response(status=status.HTTP_204_NO_CONTENT)

Traceback without self:

django_1  |   File "/usr/local/lib/python3.6/site-packages/django/core/handlers/exception.py", line 41, in inner
django_1  |     response = get_response(request)
django_1  |   File "/usr/local/lib/python3.6/site-packages/django/core/handlers/base.py", line 187, in _get_response
django_1  |     response = self.process_exception_by_middleware(e, request)
django_1  |   File "/usr/local/lib/python3.6/site-packages/django/core/handlers/base.py", line 185, in _get_response
django_1  |     response = wrapped_callback(request, *callback_args, **callback_kwargs)
django_1  |   File "/usr/local/lib/python3.6/site-packages/django/views/decorators/csrf.py", line 58, in wrapped_view
django_1  |     return view_func(*args, **kwargs)
django_1  |   File "/usr/local/lib/python3.6/site-packages/django/views/generic/base.py", line 68, in view
django_1  |     return self.dispatch(request, *args, **kwargs)
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/views.py", line 489, in dispatch
django_1  |     response = self.handle_exception(exc)
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/views.py", line 449, in handle_exception
django_1  |     self.raise_uncaught_exception(exc)
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/views.py", line 486, in dispatch
django_1  |     response = handler(request, *args, **kwargs)
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/schemas/views.py", line 31, in get
django_1  |     schema = self.schema_generator.get_schema(request, self.public)
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/schemas/generators.py", line 279, in get_schema
django_1  |     links = self.get_links(None if public else request)
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/schemas/generators.py", line 317, in get_links
django_1  |     link = view.schema.get_link(path, method, base_url=self.url)
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/schemas/inspectors.py", line 167, in get_link
django_1  |     fields += self.get_serializer_fields(path, method)
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/schemas/inspectors.py", line 290, in get_serializer_fields
django_1  |     serializer = view.get_serializer()
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/generics.py", line 110, in get_serializer
django_1  |     serializer_class = self.get_serializer_class()
django_1  |   File "/code/backend/views.py", line 173, in get_serializer_class
django_1  |     if request.method == 'POST':
django_1  | NameError: name 'request' is not defined

Traceback with self:

django_1  | Traceback (most recent call last):
django_1  |   File "/usr/local/lib/python3.6/site-packages/django/core/handlers/exception.py", line 41, in inner
django_1  |     response = get_response(request)
django_1  |   File "/usr/local/lib/python3.6/site-packages/django/core/handlers/base.py", line 187, in _get_response
django_1  |     response = self.process_exception_by_middleware(e, request)
django_1  |   File "/usr/local/lib/python3.6/site-packages/django/core/handlers/base.py", line 185, in _get_response
django_1  |     response = wrapped_callback(request, *callback_args, **callback_kwargs)
django_1  |   File "/usr/local/lib/python3.6/site-packages/django/views/decorators/csrf.py", line 58, in wrapped_view
django_1  |     return view_func(*args, **kwargs)
django_1  |   File "/usr/local/lib/python3.6/site-packages/django/views/generic/base.py", line 68, in view
django_1  |     return self.dispatch(request, *args, **kwargs)
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/views.py", line 489, in dispatch
django_1  |     response = self.handle_exception(exc)
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/views.py", line 449, in handle_exception
django_1  |     self.raise_uncaught_exception(exc)
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/views.py", line 486, in dispatch
django_1  |     response = handler(request, *args, **kwargs)
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/schemas/views.py", line 31, in get
django_1  |     schema = self.schema_generator.get_schema(request, self.public)
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/schemas/generators.py", line 279, in get_schema
django_1  |     links = self.get_links(None if public else request)
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/schemas/generators.py", line 317, in get_links
django_1  |     link = view.schema.get_link(path, method, base_url=self.url)
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/schemas/inspectors.py", line 167, in get_link
django_1  |     fields += self.get_serializer_fields(path, method)
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/schemas/inspectors.py", line 290, in get_serializer_fields
django_1  |     serializer = view.get_serializer()
django_1  |   File "/usr/local/lib/python3.6/site-packages/rest_framework/generics.py", line 110, in get_serializer
django_1  |     serializer_class = self.get_serializer_class()
django_1  |   File "/code/backend/views.py", line 173, in get_serializer_class
django_1  |     if self.request.method == 'POST':
django_1  | AttributeError: 'NoneType' object has no attribute 'method'

Answer 1

You are using a function decorator with a class based view. This will cause undefined behaviour down the line, since the class instance will not be initialized correctly.

@permission_classes([UserPermission])
class UserObject(GenericAPIView):
    ...

Instead use a class property.

class UserObject(GenericAPIView):
    permission_classes = [UserPermission]

Docs: http://www.django-rest-framework.org/api-guide/permissions/#setting-the-permission-policy

Answer 2

Remove the get_serializer_class method and you're good to go.

Modifications :

class UserObject(GenericAPIView):
    serializer_class = ObjectSerializer

    def post(self, request, user_id):
        # this is here you change the serializer.
        serializer = ObjectPostSerializer(data=request.data)
        if serializer.is_valid():
            serializer.save(user_id=user_id)
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

Answer 3

我会将视图分离为 CreateAPIView 和 RetreiveAPIView 并为它们中的每一个使用不同的序列化程序。