DRF，将自定义字段添加到 ModelSerializer

Question

我的项目中有一些模型，我需要 API 的特殊响应，我正在使用 Django Rest 框架。

class Goal(models.Model):
    name = models.CharField()
    # more fields

class Task(models.Model):
    name = models.CharField()
    goal = models.ForeignKey(Goal)

class UserTask(models.Model):
    goal = models.ForeignKey(Goal)
    user = models.ForeignKey(User)
    # other fields

我有这样的回应：

{
  "name": "One goal",
  "task": [
    {
      "name": "first task"
    },
    {
      "name": "second tas"
    }
  ]
}

但我需要这个：

{
  "name": "One goal",
  "task": [
    {
      "name": "first task",
      "is_in_usertask": true
    },
    {
      "name": "second tas",
      "is_in_usertask": false
    }
  ]
}

我在 DRF 文档中看到了这一点，但我不知道如何按UserTask当前用户（或 URL 参数中给出的其他用户）和每个Goal.

编辑：

# serializers

class TaskSerializer(serializers.ModelSerializer):
    class Meta:
        model = Task


class GoalSerializer(serializers.ModelSerializer):
    # related_name works fine
    tasks = TaskSerializer(many=True)

    class Meta:
        model = Goal

Answer 1

尝试使用SerializerMethodField字段作为

class TaskSerializer(serializers.ModelSerializer):
    is_in_usertask = serializers.SerializerMethodField(read_only=True)

    class Meta:
        model = Task
        fields = ('name', 'is_in_usertask')

    def get_is_in_usertask(self, task):
        return UserTask.objects.filter(user=self.context['request'].user, goal=task.goal).exists()