Pass request context to serializer from Viewset in Django Rest Framework

Question

I have a case where the values for a serializer field depend on the identity of the currently logged in user. I have seen how to add the user to the context when initializing a serializer, but I am not sure how to do this when using a ViewSet, as you only supply the serializer class and not the actual serializer instance.

Basically I would like to know how to go from:

class myModelViewSet(ModelViewSet):
   queryset = myModel.objects.all()
   permission_classes = [DjangoModelPermissions]
   serializer_class = myModelSerializer

to:

class myModelSerializer(serializers.ModelSerializer):
    uploaded_by = serializers.SerializerMethodField()
    special_field = serializers.SerializerMethodField()

    class Meta:
        model = myModel

    def get_special_field(self, obj):
        if self.context['request'].user.has_perm('something.add_something'):
           return something

Sorry if it wasn't clear, from the DOCs: Adding Extra Context Which says to do

serializer = AccountSerializer(account, context={'request': request})
serializer.data

But I am not sure how to do that automatically from the viewset, as I only can change the serializer class, and not the serializer instance itself.

Uncommon

Have you tried self.context.get('request').user.has_perm("some.permission") ? – Row

Do you want something to be returned with other fields of serializer in the output? – Juliajulian

Sorry if it wasn't clear, the problem is that self.context is empty in the serializer. – Uncommon

AccountSerializer(account, context={'request': request}) was all I needed for my purpose – Scratch

citynorman Where do u define request? I try to define request as: context={'request': { 'user': self.admins[0].user }} and it doesn't work! – Liberalize

Answer 1

GenericViewSet has the get_serializer_context method which will let you update context:

class MyModelViewSet(ModelViewSet):
    queryset = MyModel.objects.all()
    permission_classes = [DjangoModelPermissions]
    serializer_class = MyModelSerializer

    def get_serializer_context(self):
        context = super().get_serializer_context()
        context.update({"request": self.request})
        return context

For Python 2.7, use context = super(MyModelViewSet, self).get_serializer_context()

Grind

Selecting this as the best answer. I believe this would have solved my problem (if this is what my problem actually was). Turns out I missed the fact that I was manually instantiating the serializer in this case, and it wasn't being routed by the viewset. D'oh. – Uncommon

for me it says : NameError: name 'request' is not defined – Ellenaellender

@Ellenaellender did you fix that? That's what I get :/ context is not passed to serializer – Pneumothorax

@Bradley Neil Reed Do you have self.request? – Gorey

The latest DRF includes self.request in the default context sent to serializers; you don't need to manually add it in. – Scrimshaw

For everyone who's getting the request KeyError: You can solve this is by initializing the serializer from the view with the request object as follows: serializer = serializers.RandomSerializer(data=request.data, context={'request':request}) Source: django-rest-framework.org/api-guide/serializers/… – Thyroid

@Syslo, please could you help me look into this, it is a similar question but the solution here doesn't work for me. #62039805 – Kbp

Use self.context.request in 3.12.4. – Imperative

Answer 2

For Function based views you can pass request or user as follows:

serializer = ProductSerializer(context = {"request": request}, data=request.data)

Your Serializer may look like:

class ProductSerializer(serializers.ModelSerializer):
    class Meta:
        model = Product
        fields = ["id"]

    def create(self, validated_data):
        user = self.context["request"].user
        print(f"User is: {user}")

Feel free to inform if there is any better way to do this.

Cloison

Answer 3

just use get_serializer() in your viewsets

def get_serializer(self, *args, **kwargs):
    """
    Return the serializer instance that should be used for validating and
    deserializing input, and for serializing output.
    """
    serializer_class = self.get_serializer_class()
    kwargs['context'] = self.get_serializer_context()
    return serializer_class(*args, **kwargs)

Lafollette

your ViewSet should be subclass of GenericViewSet – Lafollette

Answer 4

Return parent context in overrided function get_serializer_context will make it easy to access request and its data.

 class myModelViewSet(ModelViewSet):
       queryset = myModel.objects.all()
       permission_classes = [DjangoModelPermissions]
       serializer_class = myModelSerializer

       def get_serializer_context(self):
       """
       pass request attribute to serializer
       """
           context = super(myModelViewSet, self).get_serializer_context()
           return context

This is very stable as every time we request viewset, it returns context as well.

Diapositive

Answer 5

the values for a serializer field depend on the identity of the currently logged in user

This is how I handle such cases in my ModelViewSet:

def perform_create(self, serializer):

    user = self.request.user
    if user.username == 'myuser':
        serializer.data['myfield'] = 'something'

    serializer.save()

Septi

Answer 6

Simply add this 2 line method in your class and you are good to go.

def get_serializer_context(self):
    return {'request': self.request}

Excruciating

Answer 7

since the posted answers had partial correctness, summarizing here in the interest of completeness.

1. override get_serializer_context..AND
2. use get_serializer in your views instead of manually calling the serializer

Floatplane

Answer 8

In my case, I could fix it by replacing the serializer definition

class MyListView(APIView):
    serializer_class = YourSerializerClass

    def get(self, request):
        queryset = self.get_queryset()
        serializer = self.serializer_class(queryset, many=True) #replace this
        return Response(serializer.data)

replace the serializer with

serializer = self.get_serializer(queryset, many=True)

Doi