permission_classes doesn't work . where is problem? - permissions

Question

I'm trying to found how Restframework's permission work , so i try write some code that response a simple Json. But the existence or absence of a ‍permission_classes does not affect the execution of the code and endpoint will response all request without checking any permission.
here is my code:
class TeacherStatisticPost(generics.RetrieveAPIView):
permission_classes = (ClassOwnerPermission)
queryset = ClassRoom.objects.all()
lookup_field = "id"
lookup_url_kwarg = 'classRoom_id'
def get_klass(self):
class_id = self.kwargs['classRoom_id']
return ClassRoom.objects.get(id=classRoom_id)
def get(self, request, *arg, **kwargs):
klass = self.get_klass()
response ={
'class_room_grade' : klass.grade,
'class_room_name' : klass.name,
}
return JsonResponse(response, safe=False)
and here is my permission.py:
class ClassOwnerPermission(permissions.BasePermission):
def has_perm(self, user, klass):
print("now in class perm") # never print out any thing!
return klass.owner == user
def has_object_permission(self, request, view, obj): # where is come from 'obj' ?
return self.has_perm(request.user, obj)
im try to set permission that just owner of ClassRoom can access to this endpoint.

Answer 1

Firstly, DRF expects permission_classes to be list or tuple. permission_classes at the line permission_classes = (ClassOwnerPermission) is not neither tuple not list. Put comma after the ClassOwnerPermission.
The line permission_classes = (ClassOwnerPermission, ) should work.
Secondly, you do not use get_object method which checks the permissions. Remove def get_klass(self): method and use get_object
Your view should look like following:
class TeacherStatisticPost(generics.RetrieveAPIView):
permission_classes = (ClassOwnerPermission, )
queryset = ClassRoom.objects.all()
lookup_field = "id"
lookup_url_kwarg = 'classRoom_id'
def get(self, request, *arg, **kwargs):
klass = self.get_object()
response ={
'class_room_grade' : klass.grade,
'class_room_name' : klass.name,
}
return JsonResponse(response, safe=False)