How to save a ModelSerializer with a foreign Key in Django Rest Framework

Question

I have these serializers

class OwnerSerializer(serializers.ModelSerializer):
    class Meta:
        model = User
        fields = [
            'id',
            'name'
        ]


class PetSerializer(serializers.ModelSerializer):
    owner = OwnerSerializer(many=False, read_only=False)

    class Meta:
        model = Pet
        fields = [
            'id',
            'name',
            'owner'
        ]

    def create(self, validated_data):
        """
        Create and return a new `Pet` instance, given the validated data.
        """
        owner_data = validated_data.pop('owner', None)
        if owner_data:
            owner = User.objects.get(**owner_data)
            validated_data['owner'] = owner
        return Pet.objects.create(**validated_data)

This is my ViewSet :

class PetViewSet(viewsets.ModelViewSet):
    """
    ModelViewSet for model pets
    """
    queryset = Pet.objects.all()
    serializer_class = PetSerializer

    def create(self, request, *args, **kwargs):
        request.data['owner'] = {'id': request.user.id, 'name': request.user.name}
        pet_serializer = self.get_serializer(data=request.data)
        pet_serializer.is_valid(raise_exception=True)
        self.perform_create(pet_serializer)
        headers = self.get_success_headers(pet_serializer.data)
        return Response(pet_serializer.data, status=status.HTTP_201_CREATED, headers=headers)

But when storing it, all the data is saved, but in the created function the owner object does not arrive, it is shown as 'owner': OrderedDict ()}

So when I return the saved object, I get it with the owner with the default id, although the user I get in the view is 'owner': {'id': 10, 'name': 'My name'}} ):

My Json Response :

{
    "id": 26,
    "name": "My pet",
    "owner": {
        "id": 1
    }
}

What am I doing wrong? Thank you

Answer 1

.get returns one item and if it matched more, It raises an expception.

owner = User.objects.get(**owner_data) , remove the trailing [0]

EDIT: Since this was not your problem, I'll tell you the problem

You're overriding create which have the validated_data , You assumed that the owner is validated but it may wrong. Do the same logic in a method named validate_owner(self, value) in which value is the value you passed for owner in the POST before it gets validated.

Answer 2

It looks to me like it's returning normalized data of the owner object, rather than the relation.

Instead of owner = OwnerSerializer() try something like: owner = PrimaryKeyRelatedField(queryset=Owner.objects.all())

Answer 3

I made the next changes in my Serializers ,the main changes was in the OwnerSerializer, 'cause the id was read only for default.

class OwnerSerializer(serializers.ModelSerializer):
    class Meta:
        model = User
        fields = [
            'id',
            'name'
        ]
        extra_kwargs = {
            'id': {
                'read_only': False,
                'required': True
            }
        }


class PetSerializer(serializers.ModelSerializer):
    owner = OwnerSerializer(many=False, read_only=False)

    class Meta:
        model = Pet
        fields = [
            'id',
            'name',
            'owner'
        ]

    def create(self, validated_data):
        """
        Create and return a new `Pet` instance, given the validated data.
        """
        owner_data = validated_data.pop('owner', None)
        if owner_data:
            owner = User.objects.get(**owner_data)
            validated_data['owner'] = owner
        return Pet.objects.create(**validated_data)