python - How to serialize only certain elements of M2M set of the object being serialized?

Question

So I have these models:

class Group(models.Model):
    name = models.CharField(max_length=255, blank=True, null=True, default=None)


class Member(models.Model):
    name = models.CharField(max_length=255, blank=True, null=True, default=None)
    group = models.ForeignKey(Group, related_name='members', on_delete=models.CASCADE)
    is_deleted = models.BooleanField()

And these serializers:

class GroupSerializer(serializers.ModelSerializer):
    members = MemberSerializer(many=True, read_only=True)

    class Meta:
        model = Group
        fields = '__all__'


class MemberSerializer(serializers.ModelSerializer):
    # some field defintions here

    class Meta:
        model = Member
        fields = '__all__'

And view:

class GroupViewSet(viewsets.ModelViewSet):
    queryset = Group.objects.all()
    serializer_class = GroupSerializer

Now what I want to do basically, is not return "members" of Group that has is_deleted set to True.

So if I have a Group with 3 Member where 1 has is_deleted set to True, I want my serializer to return the Group with 2 Members.

How do I go about achieving this?

Answer 1

To achieve this you can override the members field in the GroupSerializer to return a filtered queryset

class GroupSerializer(serializers.ModelSerializer):
    members = serializers.SerializerMethodField()

    def get_members(self, obj):
        qs = Members.objects.filter(group=obj, is_deleted=True)
        serialized = MemberSerializer(qs, many=True)
        return serialized.data

    class Meta:
        model = Group
        fields = '__all__'

This will return the member objects with is_deleted=True for the specific group.