Django Rest Framework

April 15, 2018 | 4 Minute Read

Django is Python’s killer app and DRF is Django’s killer app.

Django Rest Framework, DRF, is a framework that can be used to easily create API endpoints in your django application. If you’d like to learn more about it, I’d highly reccomend checking out the documentation and the tutorial.

This post simply records what I thought of DRF, and makes note of anything I thought was particularly interesting or worth writing down so that I could look back later.

DRF does a great job of separating its modules, and as a result has a great architecture. The components are:

• Content Negotiation: Parser and Renderer
• Authentication and Denial of Service: Authentication, Permission, Throttle
• View
• Serializer

The diagram below describes how they interact when processing a request. Eventually, the View uses the deserialized object to perform some kind of operation, typically that can involve retrieving or updating some django.Model’s state, but it could also be used to start a celery task or anything else.

The tutorial takes a neat stance, starting with a Serializer, and using it in a normal Django View. The rest of the tutorial flushes out the various other aspects of DRF. I found this tutorial format very helpful since it built on pre-existing knowledge of Django instead of just throwing the developer into the deepend. If they had wanted to, they could have started out the tutorial with an APIView, and not even used a Serializer.

These APIViews extend django.View with some great functionalities. They add content negotiation via parsers and renderers which deal with the provided and expected content-types respectively. The View also handles the authentication, permissions, and throttling behavior. Note that the diagram above doesn’t show how these are part of the view. I thought it was clearer to simply explain their implementation here. It provides a common Request object to users of the view that provides an abstraction away from the original content type. Users return rest_framework.Responses, these use a Renderer to generate rendered_content which is then finally returned to the client.

APIView is implemented as a subclass of django.View, it overrides the dispatch method to insert all of its behavior:

• version management
• content negotiation
• Request generation from HttpRequest
• authentication, permissions, throttling
• calling the correct method
• custom exception handling
• massage the final response

The APIView is further extended by a GenericAPIView which provides an interface with Django models through the .queryset attribute and Serializers with the .serializer_class attribute. It also manages some extra functionality around Filters and Pagination.

Several Mixins are present that provide common functionality, ie)

• list
• create

The more common combinations of Mixins have already been created, ie) RetrieveUpdateDestroyAPIView and ListCreateAPIView.

Instead of separating views, you can group them into a ViewSet, all this is is a way to consolidate similar View setup into one class. The way it works is by exposing an as_view class method which binds http methods to actions on the View. Thus, allowing us to basically have multiple views in one. This can be easily added to url configuration with the help of a Router, which automatically determine the url configuration of the viewset.

A lot of the magic bits of DRF revolve around the automatic introspection of models, with the ModelSerializer.

The Serializer uses a MetaClass to setup the fields provided by viewing the attrs variable on each class it’s applied to. Attributes from the Meta class are merely retrieved by getting the attribute from the ‘Meta’ attribute. to_internal_value and to_representation are defined to provide conversion. The ModelSerializer is a fun ride, but at its core uses a mapping of Model Fields to drf.Fields to arrive at a serializer.

A future post could go more in depth into:

• Specifics of serialization and Model introspection
• Analogies with Django Forms
• Comparison to other Serialization frameworks

Popular Extensions

• Creation
  • Bulk
  • Multiple Models
• Router
  • Nested
  • A lot of ‘em