django-rest-framework: add additional permission in ViewSet update method

Question

I have the following code:

class UsersViewSet(viewsets.ModelViewSet):
    model = Users
    permission_classes = (IsAuthenticated,)

    def update(self, request, *args, **kwargs):
        return super(UsersViewSet, self).update(request, *args, **kwargs)

The question is:

• how can I add additional Permission only for update method? (need to get isAuthenticated + Permission)
• overwrite permissions only for update method? (need to get only Permission without isAuthenticated) other methods in viewset should have IsAuthenticated permission

Can I make it with decorator?Or anything else?

Wanna get something like that:

@permission_classes((IsAuthenticated, AdditionalPermission ))
def update:
    pass

But if i write this code the second permission is not checked through request

Answer 1

LATER EDIT

As it seems that DRF decorators don't really work (at least not for me), this is the best solution I could come up with:

def get_permissions(self):
    # Your logic should be all here
    if self.request.method == 'GET':
        self.permission_classes = [DummyPermission, ]
    else:
        self.permission_classes = [IsAuthenticated, ]

    return super(UsersViewSet, self).get_permissions()

This actually works for both cases that you asked, but requires a bit more work. However, I've tested it and it does the job.

ORIGINAL ANSWER BELOW

There is a small mistake in the docs, you should be sending a list to the decorator (not a tuple). So it should be like this:

@permission_classes([IsAuthenticated, AdditionalPermission, ])
def update:
    pass

To answer your questions:

how can I add additional Permission only for update method?

First of all, you should know that DRF first checks for global permissions (those from the settings file), then for view permissions (declared in permission_classes -- if these exist, they will override global permissions) and only after that for method permissions (declared with the decorator @permission_classes). So another way to do the above is like this:

@permission_classes([AdditionalPermission, ])
def update:
    pass

Since ISAuthenticated is already set on the entire view, it will always be checked BEFORE any other permission.

overwrite permissions only for update method?

Well, this is hard(er), but not impossible. You can:

• set the permissions for each method and remove it from the class
• modify your AdditionalPermission class so that it also checks for user authentication if the method is not update.

Good luck.

Answer 2

You can also specify permissions for specific methods in the get_permissions() method:

class MyViewSet(viewsets.ModelViewSet):

    def get_permissions(self):
        if self.action in ('update', 'other_viewset_method'):
            self.permission_classes = [permissions.CustomPermissions,]
        return super(self.__class__, self).get_permissions()