Nested Serializers in DRF

Охватываемые темы: Reading Nested Objects, Write by ID, Read as Object, Nested List (Reverse Relation), Writing Nested Objects.

Reading Nested Objects

class ProjectSerializer(serializers.ModelSerializer):
    class Meta:
        model = Project
        fields = ['id', 'name']

class TaskSerializer(serializers.ModelSerializer):
    project = ProjectSerializer(read_only=True)  # nested object

    class Meta:
        model = Task
        fields = ['id', 'title', 'status', 'project']

API response:

{
  "id": 1,
  "title": "Task",
  "project": {"id": 5, "name": "My Project"}
}

Write by ID, Read as Object

class TaskSerializer(serializers.ModelSerializer):
    project = ProjectSerializer(read_only=True)         # for GET
    project_id = serializers.PrimaryKeyRelatedField(    # for POST/PUT
        queryset=Project.objects.all(),
        source='project',
        write_only=True,
    )

    class Meta:
        model = Task
        fields = ['id', 'title', 'project', 'project_id']

Nested List (Reverse Relation)

class TaskSerializer(serializers.ModelSerializer):
    class Meta:
        model = Task
        fields = ['id', 'title', 'status']

class ProjectSerializer(serializers.ModelSerializer):
    tasks = TaskSerializer(many=True, read_only=True)  # via related_name='tasks'

    class Meta:
        model = Project
        fields = ['id', 'name', 'tasks']

Writing Nested Objects

class ProjectSerializer(serializers.ModelSerializer):
    tasks = TaskSerializer(many=True)

    class Meta:
        model = Project
        fields = ['id', 'name', 'tasks']

    def create(self, validated_data):
        tasks_data = validated_data.pop('tasks', [])
        project = Project.objects.create(**validated_data)
        for task_data in tasks_data:
            Task.objects.create(project=project, **task_data)
        return project

    def update(self, instance, validated_data):
        tasks_data = validated_data.pop('tasks', [])
        instance = super().update(instance, validated_data)
        # Update tasks...
        return instance

SerializerMethodField

class TaskSerializer(serializers.ModelSerializer):
    project_name = serializers.SerializerMethodField()

    def get_project_name(self, obj):
        return obj.project.name if obj.project else None