Implementation of Polymorphic serializer

polymorphic_serializer.py

"""
PolymorphicSerializer Implementation taken from this stack overflow answer:
https://stackoverflow.com/a/44727343/1948982

Copied here to imortalize it to remove the risk of the answer dissappearing
"""

class PolymorphicSerializer(serializers.Serializer):
    """
    Serializer to handle multiple subclasses of another class

    - `serializer_map` maps class names to their respective serializer classes
    - An extra 'type' key is expected for serialized dict representations
    """
    serializer_map = {}  # type: Dict[str, serializers.Serializer]

    def to_representation(self, obj):
        """
        Translate object to internal data representation

        Override to allow pollymorphism
        """
        type_str = obj.__class__.__name__

        try:
            serializer = self.serializer_map[type_str]
        except KeyError:
            raise ValueError(
                'Serializer for "{}" does not exist'.format(type_str),
            )

        data = serializer(obj, context=self.context).to_representation(obj)
        data['type'] = type_str
        return data

    def to_internal_value(self, data):
        """
        Validate data and initialize primitive types

        Override to allow pollymorphism
        """
        try:
            type_str = data['type']
        except KeyError:
            raise serializers.ValidationError({
                'type': 'This field is required',
            })

        try:
            serializer = self.serializer_map[type_str]
        except KeyError:
            raise serializers.ValidationError({
                'type': 'Serializer for "{}" does not exist'.format(type_str),
            })

        validated_data = serializer(context=self.context) \
            .to_internal_value(data)
        validated_data['type'] = type_str
        return validated_data

    def create(self, validated_data):
        """
        Translate validated data represenation to object

        Override to allow pollymorphism
        """
        serializer = self.serializer_map[validated_data['type']]
        return serializer(context=self.context).create(validated_data)
      
      
class ParentClassSerializer(PolymorphicSerializer):
    """
    Serializer for ParentClass objects
    """
    serializer_map = {
        ChildClass1.__name__: ChildClass1Serializer,
        ChildClass2.__name__: ChildClass2Serializer,
    }