add query parameter support for GenericAPIView get_object method from lookup_field

[legitYosal]

Checklist

• I have verified that that issue exists against the master branch of Django REST framework.
• I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• This is not a usage question. (Those should be directed to the discussion group instead.)
• This cannot be dealt with as a third party library. (We prefer new functionality to be in the form of third party libraries where possible.)
• I have reduced the issue to the simplest possible case.
• I have included a failing test as a pull request. (If you are unable to do so we can still accept the issue.)

Description

I wanted If I pass lookup_field in query parameters of URL my view accept it and return retrieved object, and I funded a solution where I added query params to the kwargs of class as you know that get_object will search kwargs for lookup_field value, I want to know if I can make a pull request out of this??

Simple Example

API example:

# views.py
class BookAPIView(GenericAPIView, RetrieveModelMixin):
    queryset = Book.objects.all()
    serializer_class = BookSerializer
    lookup_field = 'id'
    def get(self, request, *args, **kwargs):
        return self.retrieve(request, *args, **kwargs)

# urls.py
urlpatterns = [
    path('book/', BookAPIView.as_view(), name='bookApiView'), 
]

making curl -X GET "http://localhost:8000/book/?id=12" -H "accept: application/json" will return an error for cause of not passing id as a URL slug.

Solution

if we override genericAPIView like this:

# generics.py
class GenericAPIView(APIView):
    ...
    def dispatch(self, request, *args, **kwargs):
        lookup_param = request.GET.get(self.lookup_field, None)
        if lookup_param:
            kwargs[lookup_field] = lookup_param
        return Super(GenericAPIView, self).dispatch(request, *args, **kwargs)
    ...

now if lookup_field is in URL query parameters, the object will be retrieved.

[pietrotavares]

I missed this feature today as I had to split my ViewSet into two, less elegant, Views.
Also, this sounds like a somewhat common case.

Is there any chance for this PR?

[tomchristie]

We're not going to support new features at this point, beyond keeping track with Django.

There's plenty of scope for extending REST framework either in your own codebase, or through third party packages.

[pietrotavares]

Sounds very reasonable to me.

People of the future:
I'll check in with the DRF-extensions folks, you should look there (in case I forget to edit this comment to reference the new feature).

In the meanwhile, I'll leave a reference to this mixin from django-braces as it could potentially help others with a similar use case.

@tomchristie Thanks for the quick reply, feel free to lock this discussion if you wish.