How to set current user to user field in Django Re

Question

I have the following code working perfectly. I can create a Post object from DRF panel by selecting an image and a user. However I want DRF to populate the user field by the currently logged in user.

models.py

class Post(TimeStamped):
    user = models.ForeignKey(User)
    photo = models.ImageField(upload_to='upload/')
    hidden = models.BooleanField(default=False)
    upvotes = models.PositiveIntegerField(default=0)
    downvotes = models.PositiveIntegerField(default=0)
    comments = models.PositiveIntegerField(default=0)

serializers.py

class PostSerializer(serializers.ModelSerializer):
    class Meta:
        model = Post
        fields = ['id', 'user', 'photo']

views.py

class PhotoListAPIView(generics.ListCreateAPIView):
    queryset = Post.objects.filter(hidden=False)
    serializer_class = PostSerializer
    authentication_classes = (SessionAuthentication, BasicAuthentication)
    permission_classes = (IsAuthenticated,)

How can I do this?

Answer 1

It depends on your use case. If you want it to be "write-only", meaning DRF automatically populates the field on write and doesn't return the on read, the most straight-forward implementation according to the docs would be with a HiddenField:

class PhotoListAPIView(generics.ListCreateAPIView):
    user = serializers.HiddenField(
        default=serializers.CurrentUserDefault(),
    )

If you want want it to be readable, you could use a PrimaryKeyRelatedField while being careful that your serializer pre-populates the field on write - otherwise a User could set the user field pointing to some other random User.

class PhotoListAPIView(generics.ListCreateAPIView):
    user = serializers.PrimaryKeyRelatedField(
        # set it to read_only as we're handling the writing part ourselves
        read_only=True,
    )

    def perform_create(self, serializer):
        serializer.save(user=self.request.user)

Finally, note that if you're using the more verbose APIView instead of generics.ListCreateAPIView, you have to overwrite create instead of perform_create like so:

class PhotoListAPIView(generics.ListCreateAPIView):
    user = serializers.PrimaryKeyRelatedField(
        read_only=True,
    )

    def create(self, validated_data):
        # add the current User to the validated_data dict and call
        # the super method which basically only creates a model
        # instance with that data
        validated_data['user'] = self.request.user
        return super(PhotoListAPIView, self).create(validated_data)

Answer 2

Try this:

def post(self, request, format=None)

        serializer = ProjectSerializer(data=request.data)
        request.data['user'] = request.user.id


        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)

        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST

Answer 3

@DaveBensonPhillips's answer might work in your particular case for some time, but it is not very generic since it breaks OOP inheritance chain.

ListCreateAPIView inherits from CreateModelMixin which saves the serializer already. You should always strive to get the full chain of overridden methods executed unless you have a very good reason not to. This way your code stays DRY and robust against changes:

class PhotoListAPIView(generics.ListCreateAPIView):
    ...
    def perform_create(self, serializer):
        serializer.validated_data['user'] = self.request.user
        return super(PhotoListAPIView, self).perform_create(serializer)

Answer 4

You can use CurrentUserDefault:

user = serializers.PrimaryKeyRelatedField(
    read_only=True, 
    default=serializers.CurrentUserDefault()
)

See http://www.django-rest-framework.org/api-guide/validators/#currentuserdefault

Answer 5

Off the top of my head, you can just override the perform_create() method:

class PhotoListAPIView(generics.ListCreateAPIView):
    ...
    def perform_create(self, serializer):
        serializer.save(user=self.request.user)

Give that a shot and let me know if it works

Answer 6

You will have to override the default behavior of how generics.ListCreateAPIView creates an object.

class PhotoListAPIView(generics.ListCreateAPIView):
    queryset = Post.objects.filter(hidden=False)
    authentication_classes = (SessionAuthentication, BasicAuthentication)
    permission_classes = (IsAuthenticated,)

    def get_serializer_class(self):
        if self.request.method == 'POST':
            return CreatePostSerializer
        else:
            return ListPostSerializer

    def create(self, request, *args, **kwargs):
        # Copy parsed content from HTTP request
        data = request.data.copy()

        # Add id of currently logged user
        data['user'] = request.user.id

        # Default behavior but pass our modified data instead
        serializer = self.get_serializer(data=data)
        serializer.is_valid(raise_exception=True)
        self.perform_create(serializer)
        headers = self.get_success_headers(serializer.data)
        return Response(serializer.data, status=status.HTTP_201_CREATED, headers=headers)

The .get_serializer_class() is not necessary as you can specify which fields are read-only from your serializer, but based on the projects I have worked on, I usually end up with 'asymmetric' serializers, i.e. different serializers depending on the intended operation.