How to manage serializers in Django Rest Framework?

Question

I use the following serializer in my ViewSet to create some Instance:

class InstanceCreateSerializer(ModelSerializer):
    class Meta:
        model = Instance
        fields = [
            "id",
            "name", "description", "company",
            "err_msg", "is_valid",
        ]

---

The fields author, company, is_valid and err_msg must be set by the service, not by the user. But if i use read_only_fields, as in the code below, then these fields cannot be changed by the service either.

class InstanceCreateSerializer(ModelSerializer):
    class Meta:
        model = Instance
        fields = [
            "id",
            "name", "description",
            "author", "company",
            "err_msg", "is_valid",
        ]
        read_only_fields = [
            "author", "company",
            "err_msg", "is_valid", 
        ]

---

How can I manage serializers or prevent the user from submitting values for these fields?

---

Additionally, these fields are available for input in the DRF Browsable API and Swagger, which is something I also want to fix.

Answer 1

You can use the HiddenField to not accept any data from user but populate it in validated_data.

For example, you want the current user to be set as the author for your model. You can use HiddenField like this.

class InstanceCreateSerializer(ModelSerializer):
    author = serializers.HiddenField(default=serializers.CurrentUserDefault())

    class Meta:
        model = Instance
        fields = [
            ...
            "author",
        ]

As mentioned by others, you can also use validate method to validate/set your values.

class InstanceCreateSerializer(ModelSerializer):
    ...

    def validate(self, attrs: dict) -> dict:
        attrs["company"] = attrs["author"].company
        return attrs

If you want to set values only while creating/updating, use the respective create or update methods.

class InstanceCreateSerializer(ModelSerializer):
    ...
    def create(self, validated_data: dict):
        validated_data["company"] = validated_data["author"].company
        instance = super().create(validated_data)
        return instance

    def update(self, instance, validated_data: dict):
        validated_data["company"] = validated_data["author"].company
        instance = super().update(instance, validated_data)
        return instance