在 save 方法中创建两个对象答案

【问题标题】：Create two objects in save method在 save 方法中创建两个对象
【发布时间】：2012-06-13 11:10:16
【问题描述】：

我想覆盖一个保存方法，以便为每个保存创建两个对象，而不是一个。我将如何执行以下操作？

class Message(models.Model):
    thread = models.ForeignKey('MessageThread')
    content = models.CharField(max_length=5000)
    sender = models.ForeignKey(UserProfile, related_name='message_sender')

    # filled in automatically on save()
    timestamp = models.DateTimeField(auto_now_add=True)
    recipient = models.ForeignKey(UserProfile, related_name='message_recipient')
    status = models.CharField(choices=MESSAGE_STATUS, max_length=64, default='unread')

    def save(self, *args, **kwargs):
        """
        When a message is created, this will save TWO objects of it.
        """
        sender = self.sender
        thread_initiator = self.thread.initiator
        thread_recipient = self.thread.recipient
        if sender == thread_recipient:
            self.recipient = thread_initiator
        else:
            self.recipient = thread_recipient
        self.status = 'unread' 
        super(Message, self).save(*args, **kwargs)

        # saving the second object creates an error
        Message.objects.create(thread=self.thread, content=self.content, sender=sender, recipient=sender, status='read')

--> RuntimeError: maximum recursion depth exceeded while calling a Python object

【问题讨论】：

标签： python mysql django django-models

【解决方案1】：

做两个super，如果有自动递增字段，不要忘记增加pk，否则IntegrityError会被提升。

def save(self, *args, **kwargs):
    sender = self.sender
    thread_initiator = self.thread.initiator
    thread_recipient = self.thread.recipient
    if sender == thread_recipient:
        self.recipient = thread_initiator
    else:
        self.recipient = thread_recipient
    self.status = 'unread' 
    super(Message, self).save(*args, **kwargs)

    # instead of Message.objects.create(thread=self.thread, content=self.content, sender=sender, recipient=sender, status='read')
    self.pk +=1
    self.sender = sender
    self.recipient = sender
    self.status = 'read'
    super(Message, self).save(*args, **kwargs)

【讨论】：

不要增加 pk，只需将其设为 None 并在调用 save 时让 Django 分配 pk。