django-rest-framework Serializers Getting list of all related children objects in parent's serializer

Example

Assume that, we implement a simple API and we have the following models.

class Parent(models.Model):
    name = models.CharField(max_length=50)


class Child(models.Model):
    parent = models.ForeignKey(Parent)
    child_name = models.CharField(max_length=80)

And we want to return a response when a particular parent is retrieved via API.

{
'url': 'https://dummyapidomain.com/parents/1/',
'id': '1',
'name': 'Dummy Parent Name',
'children': [{
        'id': 1,
        'child_name': 'Dummy Children I'
    },
    {
        'id': 2,
        'child_name': 'Dummy Children II'
    },
    {
        'id': 3,
        'child_name': 'Dummy Children III'
    },
    ...
],

}

For this purpose, we implement the corresponding serializers like this:

class ChildSerializer(serializers.HyperlinkedModelSerializer):

    parent_id = serializers.PrimaryKeyRelatedField(queryset=Parent.objects.all(),source='parent.id')

    class Meta:
        model = Child
        fields = ('url','id','child_name','parent_id')

    def create(self, validated_data):
        subject = Child.objects.create(parent=validated_data['parent']['id'], child_name=validated_data['child_name'])

        return child


class ParentSerializer(serializers.HyperlinkedModelSerializer):
    children = ChildSerializer(many=True, read_only=True)
    class Meta:
        model = Course
        fields = ('url','id','name','children')

To make this implementation work properly we need to update our Child model and add a related_name to parent field. Updated version of our Child model implementation should be like this:

class Child(models.Model):
parent = models.ForeignKey(Parent, related_name='children')  # <--- Add related_name here
child_name = models.CharField(max_length=80)

By doing this, we'll be able to get the list of all related children objects in parent's serializer.