In the Django REST framework, how to allow partial updates when using a ModeViewSet?

Question

I'd like to create a REST API for an object which can be partially updated. On http://www.django-rest-framework.org/api-guide/serializers/#partial-updates and example is given in which partial=True is passed when instantiating the serializer:

# Update `comment` with partial data
serializer = CommentSerializer(comment, data={'content': u'foo bar'}, partial=True)

In my case, however, the model (which is called SessionType) has the following viewset:

class SessionTypeViewSet(viewsets.ModelViewSet):
    queryset = SessionType.objects.all()
    serializer_class = SessionTypeSerializer

where the serializer is defined as

class SessionTypeSerializer(serializers.ModelSerializer):
    class Meta:
        model = SessionType
        fields = ('title',)

How can I adapt the serializer in this use case so that partial is always True?

dukebody dukebody · Accepted Answer · 2018-01-25T21:16:05

You don't need to adapt the serializer in any way. With that viewset, any call to the "detail" endpoint using the PATCH method will do a partial update.

The Django Rest Framework ModelViewSet base class includes the following mixin. Here you can see how partial=True is passed when calling partial_update, which is routed to the PATCH method by default:

class UpdateModelMixin(object):
    """
    Update a model instance.
    """
    def update(self, request, *args, **kwargs):
        partial = kwargs.pop('partial', False)
        instance = self.get_object()
        serializer = self.get_serializer(instance, data=request.data, partial=partial)
        serializer.is_valid(raise_exception=True)
        self.perform_update(serializer)

        if getattr(instance, '_prefetched_objects_cache', None):
            # If 'prefetch_related' has been applied to a queryset, we need to
            # refresh the instance from the database.
            instance = self.get_object()
            serializer = self.get_serializer(instance)

        return Response(serializer.data)

    def perform_update(self, serializer):
        serializer.save()

    def partial_update(self, request, *args, **kwargs):
        kwargs['partial'] = True
        return self.update(request, *args, **kwargs)

In the Django REST framework, how to allow partial updates when using a ModeViewSet?

2 Answers