我有一個User模型和一個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')
每個組可以有多個與之關聯的用戶，并且每個用戶可以與多個組相關聯，這在模型之間使用一個ManyToManyField和一個直通模型進行建模。當我創建組時，創建組的用戶會自動分配為組管理員，因此添加為組的成員：
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)
將創建組的用戶（組管理員）添加為成員通過覆寫的create方法成功完成GroupSerializer，然后發出POST請求，如下所示：
{
"group_name": "StackOverFlow",
"group_admin": "bigboy"
}
# which then results in the response when the group has been successfully created:
{
"group_id": 1,
"group_name": "StackOverFlow",
"group_admin": "bigboy",
"members": [
{
"username": "bigboy"
}
]
}
我希望能夠PATCH通過添加或洗掉與組關聯的用戶來通過請求更新組的成員。我試圖通過覆寫如上所示的update方法來做到這一點。請求如下所示，使用 URLGroupSerializer將用戶添加到組：PATCHhttp://127.0.0.1:8000/group/1/add/update
{
"members": [
{
"username": "small_man"
}
]
}
收到的錯誤：
line 47, in update
members_data = validated_data.pop('members') # Comes from the request body
KeyError: 'members'
我不確定我嘗試將用戶添加到組的方法是否是一種簡單甚至有效的方法，但KeyError它令人困惑，因為我假設經過驗證的資料確實包含一個members串列。
編輯
上面的錯誤已經解決。
我按如下方式覆寫了View 的perform_update方法，GroupUpdate以查看為什么我的請求資料不會被驗證：
def perform_update(self, serializer):
serializer=GroupSerializer(data=self.request.data, partial=True)
serializer.is_valid(raise_exception=True)
return super().perform_update(serializer)
出現的更詳細的錯誤是：
TypeError: Direct assignment to the reverse side of a related set is prohibited. Use user_groups.set() instead.
作為參考，user_groups 是related_name直通UserGroup模型的：
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'
)
uj5u.com熱心網友回復：
當您使用source引數時，您可以使用源值作為鍵來訪問您的資料，試試這個：
def update(self, instance, validated_data):
members_data = validated_data.pop('user_groups')
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標籤：Python django 休息 序列化 django-rest-framework
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