djangorestframework

Polymorphic serializers for Django REST Framework.

The django-rest-polymorphic package has been incorporated into django-polymorphic. This contrib package allows you to easily define serializers for your inherited models that you have created using django-polymorphic library. To migrate from django-rest-polymorphic, you need to change your import paths from rest_polymorphic.serializers to polymorphic.contrib.drf.serializers.

Usage

Define your polymorphic models:

from django.db import models

from polymorphic.models import PolymorphicModel


class Project(PolymorphicModel):
    topic = models.CharField(max_length=30)


class ArtProject(Project):
    artist = models.CharField(max_length=30)


class ResearchProject(Project):
    supervisor = models.CharField(max_length=30)

Define serializers for each polymorphic model the way you did it when you used djangorestframework:

from rest_framework import serializers

from polymorphic.contrib.drf.serializers import PolymorphicSerializer

from .models import Project, ArtProject, ResearchProject


class ProjectSerializer(serializers.ModelSerializer):
    class Meta:
        model = Project
        fields = ("topic",)


class ArtProjectSerializer(serializers.ModelSerializer):
    class Meta:
        model = ArtProject
        fields = ("topic", "artist", "url")
        extra_kwargs = {
            "url": {"view_name": "drf:project-detail", "lookup_field": "pk"},
        }


class ResearchProjectSerializer(serializers.ModelSerializer):
    class Meta:
        model = ResearchProject
        fields = ("topic", "supervisor")

Note that if you extend HyperlinkedModelSerializer instead of ModelSerializer you need to define extra_kwargs to direct the URL to the appropriate view for your polymorphic serializer.

Then you have to create a polymorphic serializer that serves as a mapper between models and serializers which you have defined above:

class ProjectPolymorphicSerializer(PolymorphicSerializer):
    model_serializer_mapping = {
        Project: ProjectSerializer,
        ArtProject: ArtProjectSerializer,
        ResearchProject: ResearchProjectSerializer,
    }

Create viewset with serializer_class equals to your polymorphic serializer:

from rest_framework import viewsets

from .models import Project
from .example_serializers import ProjectPolymorphicSerializer


class ProjectViewSet(viewsets.ModelViewSet):
    queryset = Project.objects.all()
    serializer_class = ProjectPolymorphicSerializer

Test it:

$ http GET "http://localhost:8000/projects/"

HTTP/1.0 200 OK
Content-Length: 227
Content-Type: application/json

[
    {
        "resourcetype": "Project",
        "topic": "John's gathering"
    },
    {
        "artist": "T. Turner",
        "resourcetype": "ArtProject",
        "topic": "Sculpting with Tim",
        "url": "http://localhost:8000/projects/2/"
    },
    {
        "resourcetype": "ResearchProject",
        "supervisor": "Dr. Winter",
        "topic": "Swallow Aerodynamics"
    }
]

$ http POST "http://localhost:8000/projects/" resourcetype="ArtProject" topic="Guernica" artist="Picasso"

HTTP/1.0 201 Created
Content-Length: 67
Content-Type: application/json

{
    "artist": "Picasso",
    "resourcetype": "ArtProject",
    "topic": "Guernica",
    "url": "http://localhost:8000/projects/4/"
}

Customize resource type

As you can see from the example above, in order to specify the type of your polymorphic model, you need to send a request with resource type field. The value of resource type should be the name of the model.

If you want to change the resource type field name from resourcetype to something else, you should override resource_type_field_name attribute:

class ProjectPolymorphicSerializer(PolymorphicSerializer):
    resource_type_field_name = 'projecttype'
    ...

If you want to change the behavior of resource type, you should override to_resource_type method:

class ProjectPolymorphicSerializer(PolymorphicSerializer):
    ...

    def to_resource_type(self, model_or_instance):
        return model_or_instance._meta.object_name.lower()

Now, the request for creating new object will look like this:

$ http POST "http://localhost:8000/projects/" projecttype="artproject" topic="Guernica" artist="Picasso"