Serialize filtered related fields in Django Rest framework-CodePudding

In my project, I have three models: Group, User and Challenge. Each user is a member of some groups and each challenge is intended for one or more groups.

class Group(TimeStampedModel):
    name = models.CharField(max_length=255)

class User(AbstractUser):
    user_groups = models.ManyToManyField(Group)

class Challenge(TimeStampedModel):
    ...
    groups = models.ManyToManyField(Group, null=True, blank=True)

I also have a serializer for Challenge models that serializes all challenge data and related groups using a GroupSerializer.

class ChallengeSerializer(serializers.ModelSerializer):

    groups = GroupSerializer(many=True)

    class Meta:
        model = Challenge
        fields = [..., "groups"]

My current APIView for serializing list of challenges.

class ChallengeList(generics.ListAPIView):
    queryset = Challenge.objects.all()
    serializer_class = ChallengeSerializer
    permission_classes = [permissions.IsAuthenticated]
    pagination_class = PageNumberPagination

    def get_queryset(self):
        user_groups = self.request.user.user_groups.all()
        return Challenge.objects.filter(groups__in=user_groups).distinct()

When serializing a Challenge object, a list of all related groups is serialized.

Is it possible to only serialize related Group objects that are also related to our currently logged in user?

CodePudding user response：

you could use a SerializerMethodField() to filter down the Challenges groups to just the user groups. To do this you may also need to pass in serializer context as well

To set up the serializer context:

class ChallengeList(generics.ListAPIView):
...
def get_serializer_context(self):
   context = {user_groups: self.request.user.user_groups.all()}
   return context
...

Then access this context in the SerializerMethodField in your serializer

class ChallengeSerializer(serializers.ModelSerializer):

    groups_of_user = SerializerMethodField()

    class Meta:
        model = Challenge
        fields = [..., "groups_of_user"]

    def get_groups_of_user(self, challenge):
        user_groups = self.context.get('user_groups')
        groups_of_user = challenge.groups & user_groups
        return GroupSerializer(groups_of_user, many=True).data

With this implementation you could also add prefetch_related('groups') on your queryset in ChallengeList to improve performance