Django rest api DRF - ViewSet hide a field from get but include for put

Question

I have a field that I need to hide from a get put it needs to be there for a put in a Viewset, how would I achieve this?

my serialiser is as the below, the field stores data as JSON so I need to load it as JSON to perform a get. but having the original field (routing_data) there on a get will cause a 500 error, so I need to hide it from get. but when I'm using a put, it will be this field I put into.

Thanks

serializers.py

class MonitoringSerializerRoutingTable(serializers.ModelSerializer):
    hostname = serializers.ReadOnlyField(source='device.hostname', )
    site_id = serializers.ReadOnlyField(source='device.site_id', )
    rt = serializers.SerializerMethodField(source='routing_data',)
    use = serializers.ReadOnlyField(source='device_use.use', )

    def get_rt(self, instance):
        try:
            return json.loads(instance.routing_data)
        except:
            return instance.routing_data

    class Meta:
        model = DeviceData
        fields = ('id','site_id','device_id','hostname','use', 'timestamp', 'rt','routing_data')   

views.py

class MonitoringRoutingTableUpload(viewsets.ModelViewSet):
    queryset = DeviceData.objects.select_related('device','device_use').order_by('monitoring_order')
    serializer_class = MonitoringSerializerRoutingTable
    permission_classes = (IsAdminUser,)   
    filter_class = DeviceData
    filter_backends = (filters.SearchFilter,)
    search_fields = ('device__hostname','device_use__use') 

EDIT the update serialiser doesn't seem to be updating the data

class MonitoringRoutingTableUpload(viewsets.ModelViewSet):
    queryset = DeviceData.objects.select_related('device','device_use').order_by('monitoring_order')
    permission_classes = (IsAdminUser,)   
    filter_class = DeviceData
    filter_backends = (filters.SearchFilter,)
    search_fields = ('device__hostname','device_use__use') 
    def get_serializer_class(self):
        serializers = {
            create: MonitoringCreateSerializer,
            update: MonitoringCreateSerializer,
            list: MonitoringSerializerRoutingTable,
            retrieve: MonitoringSerializerRoutingTable,
        }
        return serializers.get(self.action)

serialiezr.py

class MonitoringSerializerRoutingTable(serializers.ModelSerializer):
    hostname = serializers.ReadOnlyField(source='device.hostname', )
    site_id = serializers.ReadOnlyField(source='device.site_id', )
    rt = serializers.SerializerMethodField(source='routing_data',)
    use = serializers.ReadOnlyField(source='device_use.use', )

    def get_rt(self, instance):
        try:
            return json.loads(instance.routing_data)
        except:
            return instance.routing_data

    class Meta:
        model = DeviceData
        fields = ('id','site_id','device_id','hostname','use', 'timestamp', 'rt')   

class MonitoringCreateSerializer(serializers.ModelSerializer):

    class Meta:
        model = DeviceData
        fields = ('id','site_id','device_id','routing_data')   

PUT request

URL: http://10.66.193.200:8100/api/rt_upload/9/
data: {"routing_data": "[{'subnet': '10.10.0.0/16', 'age': '6w3d', 'next_hop': '10.20.0.0/16'}, {'subnet': '10.30.0.0/16', 'age': '6w3d', 'next_hop': '10.40.0.0/16'}, {'subnet': '10.50.0.0/16', 'age': '6w3d'...}]"}

response from postman:

{
    "id": 9,
    "site_id": 118,
    "device_id": 460,
    "hostname": "EDGE",
    "use": "Remote Site Connectivity",
    "timestamp": "2019-05-31T10:12:58.300252",
    "rt": ""
}

Answer 1

Add write_only=True to your serializer field

or

Create two serializers one for get request and one for put request. change the serializer based on request method inside view's get_serializer_class method.

Answer 2

In this case, you can use a different serializer for get and for put/post. Create a new serializer with the fields you need, then drop the serializer_class attribute and override the get_serializer_class in the view. Something like this:

class MonitoringRoutingTableUpload(viewsets.ModelViewSet):
    ...
    def get_serializer_class(self):
        serializers = {
            create: MonitoringCreateSerializer,
            update: MonitoringCreateSerializer,
            list: MonitoringSerializerRoutingTable,
            retrieve: MonitoringSerializerRoutingTable,
        }
        return serializers.get(self.action)