Django Rest Framework Viewsets Count Foreign Key-CodePudding

I am trying to add a additional field to my modelviewset. For example, if I have 1 parent and 3 children objects, I would like parent viewset json to look like. To get the count of the children I can do something like children = Child.objects.filter(parent.id=).count(), but I'm not sure how to get the parent id inside the view set.

[
    {
        "id": 1,
        "name": "parent1",
        "child_count": 3
    }
]

models.py

class Parent(models.Model):
    name = models.CharField(max_length=100)

class Child(models.Model):
    name = models.CharField(max_length=100)
    parent = models.ForeignKey("Parent", on_delete=models.CASCADE)

views.py

class ParentViewSet(viewsets.ModelViewSet):
    serializer_class = ParentSerializer

    
    children = Child.objects.filter() # ??

    def get_queryset(self):
        queryset = Parent.objects.all().annotate(child_count=) # ??

        return queryset

serializers.py

class ParentSerializer(serializers.ModelSerializer):
    
    child_count = serializers.IntegerField()

    class Meta:
        model = Parent
        fields = ["id", "name", "child_count"]

CodePudding user response：

There may be a shorthand way to get this count- however a SerializerMethodField is pretty straightforward.

class ParentSerializer(serializers.ModelSerializer):
    child_count = serializers.SerializerMethodField()

    class Meta:
        model = Parent
        fields = ["id", "name", "child_count"]


    def get_child_count(self):
        return Child.objects.filter(parent=self.get_object()).count()