Django Rest Framework：重写序列化程序中的 'update' 函数时出现 KeyError

Question

我有一个 User 模型和一个 Group 模型，如下所示：

class User(models.Model):
    username = models.CharField(primary_key=True, max_length=32, unique=True)
    user_email = models.EmailField(max_length=32, unique=False)
    user_password = models.CharField(max_length=32)
    user_avatar_path = models.CharField(max_length=64)

class Group(models.Model):
    group_id = models.AutoField(primary_key=True)
    group_name = models.CharField(max_length=32, unique=False)
    group_admin = models.ForeignKey(User, on_delete=models.CASCADE, related_name='my_groups')
    members = models.ManyToManyField(User, related_name='groups', through='UserGroup')

每个组可以有多个用户与之关联，每个用户可以关联到多个组，这是用 ManyToManyField 和模型之间的直通模型建模的。当我创建一个组时，创建该组的用户被自动指定为组管理员，因此被添加为该组的成员：

class MemberSerializer(serializers.ModelSerializer): # The nested serializer used within the GroupSerializer

    username = serializers.ReadOnlyField(source='user.username')

    class Meta:
        model = User
        fields = ['username']

class GroupSerializer(serializers.ModelSerializer):
    members = MemberSerializer(source='user_groups', many=True, required=False)
    group_admin = serializers.SlugRelatedField(slug_field='username', queryset=User.objects.all()) # A Group object is related to a User object by username

    class Meta:
        model = Group
        fields = ['group_id', 'group_name', 'group_admin', 'members']

    def create(self, validated_data): # Overriden so that when a group is created, the group admin is automatically declared as a member.
        group = Group.objects.create(**validated_data)
        group_admin_data = validated_data.pop('group_admin')
        group.members.add(group_admin_data)

        return group

    def update(self, instance, validated_data):
        members_data = validated_data.pop('members') # Comes from the request body
        group_id = self.kwargs['group_id'] # Comes from the URL
        add_remove = self.kwargs['add_remove'] # Comes from the URL 
        group = Group.objects.filter(group_id=group_id).first()
        if members_data is not None:
            if add_remove == 'add':
                for member in members_data:
                    group.members.add(member['username'])
            elif add_remove == 'remove':
                for member in members_data:
                    group.members.remove(member['username'])   
            
        return super().update(instance, validated_data)

通过覆盖 GroupSerializer 的 create 方法，然后发出 POST 请求，成功将创建组的用户（组管理员）添加为成员如下所示：

{
    "group_name": "Whosebug",
    "group_admin": "bigboy"  
}

# which then results in the response when the group has been successfully created:

{
    "group_id": 1,
    "group_name": "Whosebug",
    "group_admin": "bigboy",
    "members": [
        {
            "username": "bigboy"
        }
    ]
}

我希望能够通过 PATCH 请求通过添加或删除与组关联的用户来更新组成员。如上所示，我试图通过覆盖 GroupSerializer 的 update 方法来做到这一点。 PATCH 请求如下所示，使用 http://127.0.0.1:8000/group/1/add/update 的 URL 将用户添加到组：

{
    "members": [
        {
            "username": "small_man"
        }
    ]
}

收到的错误：

line 47, in update
    members_data = validated_data.pop('members') # Comes from the request body
KeyError: 'members'

我不确定我尝试将用户添加到群组的方法是否简单甚至有效，但 KeyError 令人困惑，因为我假设经过验证的数据确实包含members列表。

编辑

上面的错误已经解决。

我覆盖了 GroupUpdate 视图的 perform_update 方法，如下所示，以了解为什么我的请求数据无法验证：

    def perform_update(self, serializer):
        serializer=GroupSerializer(data=self.request.data, partial=True)
        serializer.is_valid(raise_exception=True)
        return super().perform_update(serializer)

出现的更详细的错误是： TypeError: Direct assignment to the reverse side of a related set is prohibited. Use user_groups.set() instead. 作为参考，user_groups 是 UserGroup through 模型的 related_name：

class UserGroup(models.Model): # Manually specified Junction table for User and Group
    user = models.ForeignKey(
        User, 
        on_delete=models.CASCADE, 
        related_name='user_groups'
        )
    group = models.ForeignKey(
        Group, 
        on_delete=models.CASCADE, 
        related_name='user_groups'
        )

Answer 1

当您使用 source 参数时，您可以使用源值作为键来访问您的数据，试试这个：

def update(self, instance, validated_data):
    members_data = validated_data.pop('user_groups')

Django Rest Framework：重写序列化程序中的 'update' 函数时出现 KeyError

Django Rest Framework: KeyError when Overriding 'update' Function in a Serializer

python

django

rest

serialization

django-rest-framework