Django Rest Framework 中的嵌套序列化程序“通过模型”答案

【问题标题】：Nested serializer "Through model" in Django Rest FrameworkDjango Rest Framework 中的嵌套序列化程序“通过模型”
【发布时间】：2019-01-16 10:43:30
【问题描述】：

我在序列化中间“枢轴”模型并附加到 Django Rest Framework 中多对多关系中的每个项目时遇到困难。

例子：

models.py：

class Member(models.Model):
    name = models.CharField(max_length = 20)
    groups = models.ManyToManyField('Group', through='Membership')

class Group(models.Model):
    name = models.CharField(max_length = 20)

class Membership(models.Model):
    member = models.ForeignKey('Member')
    group = models.ForeignKey('Group')
    join_date = models.DateTimeField()

serializers.py:

class MemberSerializer(ModelSerializer):
    class Meta:
        model = Member

class GroupSerializer(ModelSerializer):
    class Meta:
        model = Group

class MembershipSerializer(ModelSerializer):
    class Meta:
        model = Membership

我试图遵循答案： Include intermediary (through model) in responses in Django Rest Framework

但这并不是我所需要的

我需要生成以下输出

{
  "id": 1,
  "name": "Paul McCartney",
  "groups": [
    {
      "id": 3,
      "name": "Beatles",
      "membership": {
        "id": 2,
        "member_id": 1,
        "group_id": 3,
        "join_date": "2018-08-08T13:43:45-0300"
      }
    }
  ]
}

在此输出中，我为组中的每个项目返回相关的“通过模型”。

我怎样才能以这种方式生成序列化模型？

【问题讨论】：

标签： python django django-rest-framework

【解决方案1】：

根据您希望显示输出的方式，我建议您将模型更改为：

class Group(models.Model):
    name = models.CharField(max_length=20)
    members = models.ManyToManyField(
        'Membership',
        related_name='groups',
        related_query_name='groups',
    )


class Member(models.Model):
    name = models.CharField(max_length=20)


class Membership(models.Model):
    group = models.ForeignKey(
        'Group',
        related_name='membership',
        related_query_name='memberships',
    )
    join_date = models.DateTimeField()

Group 模型和Member 模型是ManytoMany 的，没有问题你让Group 模型中的关系。在序列化中输出它是最容易的。 related_name 和related_query_name 用于进行序列化并指向嵌套关系。

最后，你的序列化可能是这样的（我用 create 方法举例说明）：

class MembershipSerializer(ModelSerializer):
    class Meta:
        fields = ("id", "join_date",)


class GroupSerializer(ModelSerializer):
    memberships = MembershipSerializer(many=True)

    class Meta:
        model = Group
        fields = ("id", "name", "memberships",)


class MemberSerializer(ModelSerializer):
    groups = GroupSerializer(many=True)

    class Meta:
        model = Member
        fields = ("id", "name", "groups")

    def create(self):
        groups_data = validated_data.pop('groups')
        member = Member.objects.create(**validated_data)
        for group in groups_data:
            memberships_data = group.pop('memberships')
            Group.objects.create(member=member, **group)
            for memberhip in memberships:
                Membership.objects.create(group=group, **memberships)

输出将是：

{
  "id": 1,
  "name": "Paul McCartney",
  "groups": [
    {
      "id": 3,
      "name": "Beatles",
      "memberships": [
        {
          "id": 2,
          "join_date": "2018-08-08T13:43:45-0300"
        }
      ]
    }
  ]
}

在此输出中，我没有“嵌套”父 ID，但您也可以这样做，只需在字段属性中声明即可。

【讨论】：

这会删除直通模型，因此不能完全回答问题。在这种情况下它可以工作，但是对于直通模型的用例可能需要序列化。

【解决方案2】：

通过查看您的输出，您似乎想要显示组内的成员资格和成员内的组。我建议将序列化程序编辑成这样。

class MemberSerializer(ModelSerializer):
    groups = GroupSerializer(many=True)         
    class Meta:
        model = Member
        fields = ("id","name","groups")

class GroupSerializer(ModelSerializer):
    membership = MembershipSerializer()        
    class Meta:
        model = Group
        fields = ("id","name","membership")

class MembershipSerializer(ModelSerializer):
    class Meta:
        model = Membership
        fields = "__all__"

【讨论】：