Current User inside nested serializer

Question

I'm using Django Rest Framework 3.3.2 with Django 1.9.1 I have 2 serializers and I use one of them inside the other one.

class VideoSerializer(serializers.ModelSerializer):
current_username = serializers.SerializerMethodField()
is_deletable = serializers.SerializerMethodField()
tagged_users = EachUserSerializer(many=True, read_only=True)
print current_username
comments = CommentSerializer(many=True, read_only=True, context={'current_username': current_username})
place_taken = PlaceLimitedSerializer()
owner_user = EachUserSerializer()

class Meta:
    model = Video
    fields = ('tagged_users', 'comments', 'place_taken', 'video_id', 'video_url', 'like_count', 'caption', 'date',
              'category', 'owner_user', 'current_username', 'is_deletable', )

def get_current_username(self, obj):
    self.current_username = self.context['request'].user.username
    return self.context['request'].user.username

def get_is_deletable(self, obj):

    return obj.is_deletable_by(self.current_username)



class CommentSerializer(serializers.ModelSerializer):
current_username = serializers.SerializerMethodField()
is_deletable = serializers.SerializerMethodField()
is_editable = serializers.SerializerMethodField()

def get_current_username(self, obj):
    self.current_username = self.context['current_username']
    return self.current_username

def get_is_deletable(self, obj):
    return obj.is_deletable(self.current_username)

def get_is_editable(self, obj):
    return obj.is_editable(self.current_username)

class Meta:
    model = Comment
    fields = ('comment', 'username', 'comment_id', 'date', 'current_username', 'is_editable', 'is_deletable',)

My question is that I need current user's username in serializers. I managed to do that in VideoSerializer by setting a context in view like this.

class get_video(APIView):

def get(self, request):
    video_id = str(request.query_params.get('video_id'))
    if Video.objects.all().filter(video_id=video_id).exists():
        video = Video.objects.get(video_id=video_id)
        serializer = VideoSerializer(video, context={"request": request})
        return JsonResponse(serializer.data)
    else:
        return JsonResponse({"result": "no_video"})

In VideoSerializer, I tried to set context and I want to pass 'current_user' to the CommentSerializer but it gives this error.

Internal Server Error: /video/get_video/
Traceback (most recent call last):
File "/Users/mcagataybarin/molocate-dev/env/lib/python2.7/site-packages/django/core/handlers/base.py", line 149, in get_response
response = self.process_exception_by_middleware(e, request)
File "/Users/mcagataybarin/molocate-dev/env/lib/python2.7/site-packages/django/core/handlers/base.py", line 147, in get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/Users/mcagataybarin/molocate-dev/env/lib/python2.7/site-packages/django/views/decorators/csrf.py", line 58, in wrapped_view
return view_func(*args, **kwargs)
File "/Users/mcagataybarin/molocate-dev/env/lib/python2.7/site-packages/django/views/generic/base.py", line 68, in view
return self.dispatch(request, *args, **kwargs)
File "/Users/mcagataybarin/molocate-dev/env/lib/python2.7/site-packages/rest_framework/views.py", line 466, in dispatch
response = self.handle_exception(exc)
File "/Users/mcagataybarin/molocate-dev/env/lib/python2.7/site-packages/rest_framework/views.py", line 463, in dispatch
response = handler(request, *args, **kwargs)
File "/Users/mcagataybarin/molocate-dev/molocate_eb/video/views.py", line 96, in get
return JsonResponse(serializer.data)
File "/Users/mcagataybarin/molocate-dev/env/lib/python2.7/site-packages/rest_framework/serializers.py", line 503, in data
ret = super(Serializer, self).data
File "/Users/mcagataybarin/molocate-dev/env/lib/python2.7/site-packages/rest_framework/serializers.py", line 239, in data
self._data = self.to_representation(self.instance)
File "/Users/mcagataybarin/molocate-dev/env/lib/python2.7/site-packages/rest_framework/serializers.py", line 472, in to_representation
ret[field.field_name] = field.to_representation(attribute)
File "/Users/mcagataybarin/molocate-dev/env/lib/python2.7/site-packages/rest_framework/serializers.py", line 614, in to_representation
self.child.to_representation(item) for item in iterable
File "/Users/mcagataybarin/molocate-dev/env/lib/python2.7/site-packages/rest_framework/serializers.py", line 472, in to_representation
ret[field.field_name] = field.to_representation(attribute)
File "/Users/mcagataybarin/molocate-dev/env/lib/python2.7/site-packages/rest_framework/fields.py", line 1645, in to_representation
return method(value)
File "/Users/mcagataybarin/molocate-dev/molocate_eb/video/serializers.py", line 13, in get_current_username
self.current_username = self.context['current_username']
KeyError: 'current_username'

How can I fix that ? I checked the DRF documentation and also checked the stackoverflow but couldn't find the right answer. I'd appreciate if you help.

Answer 1

The context is available for anything that is under the top serializer - i.e. applies to Serializers and Fields as well. Therefore in the CommentSerializer you should have:

self.current_username = self.context['request'].user.username

Answer 2

After a lot of google search, I fixed the problem like this.

class VideoSerializer(serializers.ModelSerializer):
    current_username = serializers.SerializerMethodField()
    is_deletable = serializers.SerializerMethodField()
    tagged_users = EachUserSerializer(many=True, read_only=True)
    comments = serializers.SerializerMethodField()
    place_taken = PlaceLimitedSerializer()
    owner_user = EachUserSerializer()

    class Meta:
        model = Video
        field = ('tagged_users', 'comments', 'place_taken', 'video_id', 'video_url', 'like_count', 'caption', 'date',
                  'category', 'owner_user', 'is_deletable', )

    def get_comments(self, obj):
        serializer_context = {'current_username': self.current_username}
        serializer = CommentSerializer(obj.comments, many=True, read_only=True, context=serializer_context)
        return serializer.data

    def get_current_username(self, obj):
        self.current_username = self.context['request'].user.username
        return self.context['request'].user.username

    def get_is_deletable(self, obj):

        return obj.is_deletable_by(self.current_username)

    class CommentSerializer(serializers.ModelSerializer):
    current_username = serializers.SerializerMethodField()
    is_deletable = serializers.SerializerMethodField()
    is_editable = serializers.SerializerMethodField()

    def get_current_username(self, obj):
        self.current_username = self.context.get('current_username')
        return self.context.get('current_username')

    def get_is_deletable(self, obj):
        return obj.is_deletable(self.current_username)

    def get_is_editable(self, obj):
        return obj.is_editable(self.current_username)

    class Meta:
        model = Comment
        fields = ('comment', 'username', 'comment_id', 'date', 'current_username', 'is_editable', 'is_deletable',)

I serialized the nested serialization inside SerializerMethodField and I've sent the current_username that I extract from context to the nester serializer's context. After doing this problem solved and it works :)