Django Rest Framework: How to Dynamically return subset of fields

Question

I would like to filter by fields name and get back a subset instead of having back all my fields name. For example here I am filtering by id and name. It should return me only this two dimension in json format. I have found many solution on the site and I have done exactly the same as suggested but I don't have the expected result. Could you please help me ?

my urls.py:

router = routers.DefaultRouter()
urlpatterns = [
    path('', include(router.urls)),
    path('edges/', edge_list),
    path('edges/<int:pk>/', edge_detail),
    path('network/<int:pk>/edges/', edges_of_a_network),
]

my view

@api_view(['GET', 'POST'])
def edge_list(request):
    """
    List all edges of all networks, or create a new edge.
    """
    if request.method == 'GET':
        edges = Edge.objects.all()
        serializer = EdgeSerializer(edges, many=True)
        return Response(serializer.data)

    elif request.method == 'POST':
        serializer = EdgeSerializer(data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        return Response(serializer.error, status=status.HTTP_400_BAD_REQUEST)

Here a copy past example from https://www.django-rest-framework.org/api-guide/serializers/#example

class DynamicFieldsModelSerializer(serializers.ModelSerializer):
    """
    A ModelSerializer that takes an additional `fields` argument that
    controls which fields should be displayed.
    """

    def __init__(self, *args, **kwargs):
        # Don't pass the 'fields' arg up to the superclass
        fields = kwargs.pop('fields', None)

        # Instantiate the superclass normally
        super(DynamicFieldsModelSerializer, self).__init__(*args, **kwargs)

        if fields is not None:
            # Drop any fields that are not specified in the `fields` argument.
            allowed = set(fields)
            existing = set(self.fields)
            for field_name in existing - allowed:
                self.fields.pop(field_name)

My serializer class which I would like to filter fields.

class EdgeSerializer(DynamicFieldsModelSerializer, serializers.ModelSerializer):
    source = serializers.SerializerMethodField(method_name='get_node_source')
    target = serializers.SerializerMethodField(method_name='get_node_target')
    road_type = serializers.SerializerMethodField(
                                        method_name='get_road_type_id')

    class Meta:
        model = Edge
        fields = (
            'id', 'edge_id', 'name', 'length', 'speed',
            'lanes', 'param1', 'param2', 'param3', 'network',
            'road_type', 'source', 'target'
        )

    def get_road_type_id(self, instance):
        return {"id": instance.road_type.road_type_id,
                "name": instance.road_type.name}

    def get_node_source(self, instance):
        return {"node_id":instance.source.node_id, "node_name": instance.source.name}

    def get_node_target(self, instance):
        return {"node_id":instance.target.node_id, "node_name": instance.target.name}

Answer 1

How are you consuming the serializer in your view? You can initialize as:

fields = request.query_params.get('fields')
fields_cleaned = [field.replace('-', '') for field in fields]
ser = EdgeSerializer(fields=fields_cleaned, instance=queryset, many=True)
print(ser.data)

Answer 2

@api_view(['GET', 'POST'])
def edge_list(request):
    """
    List all edges of all networks, or create a new edge.
    """
    if request.method == 'GET':
        edges = Edge.objects.all()
        fields = request.query_params.get('fields')
        fields_cleaned = [field.replace('-', '') for field in fields]
        if not fields_cleaned:
            serializer = EdgeSerializer(fields=fields, instance=edges, many=True)
        else:
            serializer = EdgeSerializer(instance=edges, many=True)
        return Response(serializer.data)

    elif request.method == 'POST':
        serializer = EdgeSerializer(data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        return Response(serializer.error, status=status.HTTP_400_BAD_REQUEST)