Django Rest Framework modelviewset - updating fields before create

Question

I have a modelviewset:

class ExpenseViewSet(ModelViewSet):
    permission_classes = [permissions.IsAuthenticated, HasMetis]
    serializer_class = ExpenseSerializer

    def get_queryset(self):
        return Expense.objects.filter(recorded_by=self.request.user)

And a serializer:

class ExpenseSerializer(serializers.ModelSerializer):
    class Meta:
        model = Expense
        fields = ["flat_id", "flat_group_id", "description", "notes", "amount"]

These are the fields that are POSTed to the viewset, but they are not sufficient to populate the object completely, so I need to add some more fields.

I've tried overriding the serializer, like so:

class ExpenseSerializer(serializers.ModelSerializer):
    class Meta:
        model = Expense
        fields = ["flat_id", "flat_group_id", "description", "notes", "amount"]

    def create(self, validated_data):
        expense = Expense.objects.create(
            flat_id=validated_data["operations_flat"],
            flat_group_id=validated_data["operations_building"],
            description=validated_data["description"],
            notes=validated_data["notes"],
            amount=validated_data["amount"],
            recorded_by=self.request.user,
        )
        return expense

This, however, is never called (tested by sticking a print statement in the create function - it never runs). Apparently this is because of this question: Django Rest Framework serializer create() doesn't get triggered This explains the issue, but not how to solve my problem.

I'm not sure whether I need to override the is_valid function of the serializer, the create function of the serializer, or the create function of the viewset, or something else.

Might be you overrode something on the viewset that messes the default views behavior or the data you provided aren't valid (check the server response code and content). — Linovia

Umair Mohammad Umair Mohammad · Accepted Answer · 2018-12-18T05:09:58

You should override the perform_create() on viewset something like this and pass in your extra data for object creation:

def perform_create(self, serializer):
    serializer.save(user=self.request.user)

Reference : Save and deletion hooks: https://www.django-rest-framework.org/api-guide/generic-views/#genericapiview (search perform_create in this page for faster lookup)

Django Rest Framework modelviewset - updating fields before create

1 Answers