Dynamically exclude or include a field in Django REST framework serializer

Question

I have a serializer in Django REST framework defined as follows:

class QuestionSerializer(serializers.Serializer):
    id = serializers.CharField()
    question_text = QuestionTextSerializer()
    topic = TopicSerializer()

Now I have two API views that use the above serializer:

class QuestionWithTopicView(generics.RetrieveAPIView):
    # I wish to include all three fields - id, question_text
    # and topic in this API.
    serializer_class = QuestionSerializer

class QuestionWithoutTopicView(generics.RetrieveAPIView):
    # I want to exclude topic in this API.
    serializer_class = ExamHistorySerializer

One solution is to write two different serializers. But there must be a easier solution to conditionally exclude a field from a given serializer.

Answer 1

Have you tried this technique

class QuestionSerializer(serializers.Serializer):
    def __init__(self, *args, **kwargs):
        remove_fields = kwargs.pop('remove_fields', None)
        super(QuestionSerializer, self).__init__(*args, **kwargs)

        if remove_fields:
            # for multiple fields in a list
            for field_name in remove_fields:
                self.fields.pop(field_name)

class QuestionWithoutTopicView(generics.RetrieveAPIView):
        serializer_class = QuestionSerializer(remove_fields=['field_to_remove1' 'field_to_remove2'])

If not, once try it.

Answer 2

Creating a new serializer is the way to go. By conditionally removing fields in a serializer you are adding extra complexity and making you code harder to quickly diagnose. You should try to avoid mixing the responsibilities of a single class.

Following basic object oriented design principles is the way to go.

QuestionWithTopicView is a QuestionWithoutTopicView but with an additional field.

class QuestionSerializer(serializers.Serializer):
        id = serializers.CharField()
        question_text = QuestionTextSerializer()
        topic = TopicSerializer()

class TopicQuestionSerializer(QuestionSerializer):
       topic = TopicSerializer()