Django模型-循环导入问题

Question

我的Django项目使用三个应用程序chat, user, sowi。每个应用程序的模型结构如下。我在启动服务器时遇到了一个错误，我想这是因为我有循环导入。如何解决此问题？

聊天/模型.py

from user.models import User
class Chat(models.Model):
name = models.CharField(max_length=100, default="private")

class Message(models.Model):
sender = models.ForeignKey(User, on_delete=models.CASCADE)
receiver = models.ForeignKey(Chat, on_delete=models.CASCADE)

用户/型号.py

from chat.models import Chat
from sowi.models import Sowi
class User(AbstractUser):
chats = models.ManyToManyField(Chat, blank=True)
subscriptions = models.ManyToManyField(Sowi, related_name="subscriptions", blank=True)
memberships = models.ManyToManyField(Sowi, related_name="memberships", blank=True)
blocked = models.ManyToManyField("self", related_name="blocked", blank=True)

sowi/models.py

from chat.models import Chat, Message
from user.models import User
class Sowi(models.Model):
owner = models.ForeignKey(User, on_delete=models.CASCADE)
chat = models.OneToOneField(Chat, blank=True, null=True, on_delete=models.CASCADE)

错误消息：

File "*/sowi/models.py", line 9, in <module>
from chat.models import Chat, Message
File "*/chat/models.py", line 4, in <module>
from user.models import User
File "*/user/models.py", line 5, in <module>
from chat.models import Chat
ImportError: cannot import name 'Chat' from 'chat.models'

提前感谢！

Answer 1

用字符串文字引用模型比用对模型类的引用引用模型要好。Django可以处理这个问题，并将自动解决这些问题：

# chat/models.py
from django.db import models
class Chat(models.Model):
name = models.CharField(max_length=100, default="private")
class Message(models.Model):
sender = models.ForeignKey('user.User', on_delete=models.CASCADE)
receiver = models.ForeignKey(Chat, on_delete=models.CASCADE)
# user/models.py
from django.db import models
class User(AbstractUser):
chats = models.ManyToManyField(Chat, blank=True)
subscriptions = models.ManyToManyField('sowi.Sowi', related_name="subscriptions", blank=True)
memberships = models.ManyToManyField('sowi.Sowi', related_name="memberships", blank=True)
blocked = models.ManyToManyField("self", related_name="blocked", blank=True)
# sowi/models.py
from django.db import models
class Sowi(models.Model):
owner = models.ForeignKey('user.User', on_delete=models.CASCADE)
chat = models.OneToOneField('chat.Chat', blank=True, null=True, on_delete=models.CASCADE)

当你参考用户模型[Django-doc]设置AUTH_USER_MODEL设置[Django-dc]时，使用这个设置会更好，这样，如果你以后改变主意，你可以更方便地更改这个：

# chat/models.py
from django.conf import settings
from django.db import models
class Chat(models.Model):
name = models.CharField(max_length=100, default="private")
class Message(models.Model):
sender = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
receiver = models.ForeignKey(Chat, on_delete=models.CASCADE)
# user/models.py
from django.db import models
class User(AbstractUser):
chats = models.ManyToManyField(Chat, blank=True)
subscriptions = models.ManyToManyField('sowi.Sowi', related_name="subscriptions", blank=True)
memberships = models.ManyToManyField('sowi.Sowi', related_name="memberships", blank=True)
blocked = models.ManyToManyField("self", related_name="blocked", blank=True)
# sowi/models.py
from django.conf import settings
from django.db import models
class Sowi(models.Model):
owner = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
chat = models.OneToOneField('chat.Chat'

Answer 2

try:

class User(AbstractUser):
chats = models.ManyToManyField('chat.Chat', blank=True)
subscriptions = models.ManyToManyField('sowi.Sowi', related_name="subscriptions", blank=True)
memberships = models.ManyToManyField('sowi.Sowi', related_name="memberships", blank=True)
blocked = models.ManyToManyField("self", related_name="blocked", blank=True)

代码的问题是，您在用户models.py中导入Chat和Sowi，然后尝试在Chat和Sowi中导入用户models。你看到环形进口了吗？