为什么在django模式中不能使用两个独立的外键来使用相同的模型

问题描述

我有一个理论模型不工作：

class Message（models.Model）：
text = models .TextField（）
created = models.DateTimeField（auto_now_add = True）
sender = models.ForeignKey（User）
receiver = models.ForeignKey（User） / p>

现在，如果一个用户对某人发送消息，比如私人消息线程，那么你有人发送了这个消息，而有人收到了这个消息，这是很重要的。这两个都应该是一对多我认为，因为每个用户可以发送无限的消息。发件人和接收者是来自同一模型用户的用户，但他们必须是不同的人。我得到django whining关于

django.core.management.base.CommandError：系统检查确定了一些问题： / p>

错误：
chat.Message.receiver：（fields.E304）Message.receiver的反向访问者与反向访问者冲突'Message.sender'。
提示：添加或更改相关名称参数到Message.receiver或Message.sender的定义。
chat.Message.sender：（fields.E304）Message.sender的反向访问者与Message.receiver的反向访问者冲突。
提示：添加或更改Message.sender或Message.receiver定义的related_name参数。

我应该添加unique = True，因为您不能向自己发送消息？这是在用户之间实现消息的不好的方法吗？我的错误是什么？谢谢，

Cody

解决方案

对外键定义的参数：

  class Message（models.Model）： 
 text = models.TextField（）
 created = models.DateTimeField（auto_now_add = True）
 sender = models.ForeignKey（User，related_name ='messages_sent'）
 receiver = models .ForeignKey（User，related_name ='messages_received'）
  

这些相关名称可以在像这样：

  user = User.objects.get（username ='johndoe'）
 messages_from = user.messages_sent.all（）
 messages_to = user .messages_received.all（）
  

相当于：

  user = User.objects.get（username ='johndoe'）
 messages_from = Messages.objects.filter（sender = user）
 messages_to = Messages.objects.filter（receiver = user）
  

I have a theoretical model that isn't working:

class Message(models.Model): text = models.TextField() created = models.DateTimeField(auto_now_add=True) sender = models.ForeignKey(User) receiver = models.ForeignKey(User)

Now if a user messaged someone, like a private message thread, you have someone who sent it, and someone who received it, which is important to know. Both of these should be a one-to-many I think because each user can send infinite messages. Senders and receivers are users, from the same model User, but they must be different people. I get django whining about

django.core.management.base.CommandError: System check identified some issues:

ERRORS:chat.Message.receiver: (fields.E304) Reverse accessor for 'Message.receiver' clashes with reverse accessor for 'Message.sender'. HINT: Add or change a related_name argument to the definition for 'Message.receiver' or 'Message.sender'.chat.Message.sender: (fields.E304) Reverse accessor for 'Message.sender' clashes with reverse accessor for 'Message.receiver'. HINT: Add or change a related_name argument to the definition for 'Message.sender' or 'Message.receiver'.

Should I add unique=True since you can't send messages to yourself? Is this a bad way to implement messages between users? And what is my error? Thank you,

Cody

解决方案

As the error message says add the related_name argument to the foreign key definitions:

class Message(models.Model):
    text        = models.TextField()
    created     = models.DateTimeField(auto_now_add=True)
    sender      = models.ForeignKey(User, related_name='messages_sent')
    receiver    = models.ForeignKey(User, related_name='messages_received')

These related names can be used in the backward relations like this:

user = User.objects.get(username='johndoe')
messages_from = user.messages_sent.all()
messages_to = user.messages_received.all()

Which is the equivalent of:

user = User.objects.get(username='johndoe')
messages_from = Messages.objects.filter(sender=user)
messages_to = Messages.objects.filter(receiver=user)

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