python - 如何让 Django 信号调用模型方法？

Question

也许只是太晚了，但我无法弄清楚为什么这不起作用。当我有一个 post_save 信号调用一个通用函数时，它可以工作，但是当我有一个 post_save 信号调用模型中的一个方法时，什么也没有发生。这是有效的代码：

class Revision(models.Model):
    # Model junk...

def send_email(sender, instance, created, **kwargs):
    if created:
        print "DO STUFF"

signals.post_save.connect(send_email, sender=Revision)

但这不起作用：

class Revision(models.Model):
    # Model junk...

    def send_email(sender, instance, created, **kwargs):
        if created:
            print "DO STUFF"

signals.post_save.connect(Revision.send_email, sender=Revision)

有没有善良的灵魂可以阻止我把头撞到墙上？谢谢。

Answer 1

在我看来，第二个问题是您使用的是无界方法send_mail。如果您真的想send_mail在课堂上打电话，也许@classmethod或@staticmethod会帮助您：

class Revision(models.Model):
    # Model junk...

    @classmethod
    def send_email(cls, sender, instance, created, **kwargs):
        if created:
            print "DO STUFF"

signals.post_save.connect(Revision.send_email, sender=Revision)

或者

class Revision(models.Model):
    # Model junk...

    @staticmethod
    def send_email(sender, instance, created, **kwargs):
        if created:
            print "DO STUFF"

signals.post_save.connect(Revision.send_email, sender=Revision)

或者，不使用这些装饰器，您可以传递有界实例方法：

class Revision(models.Model):
# Model junk...

    def send_email(self, sender, instance, created, **kwargs):
        if created:
            print "DO STUFF"

signals.post_save.connect(Revision().send_email, sender=Revision)

---

参考：

1. 从 Django源代码：

   def connect(self, receiver, sender=None, weak=True, dispatch_uid=None):
       """
       Connect receiver to sender for signal.
   
       Arguments:
   
           receiver
               A function or an instance method which is to receive signals.
               Receivers must be hashable objects.
   
               If weak is True, then receiver must be weak-referencable (more
               precisely saferef.safeRef() must be able to create a reference
               to the receiver).
   
               Receivers must be able to accept keyword arguments.
   
               If receivers have a dispatch_uid attribute, the receiver will
               not be added if another receiver already exists with that
               dispatch_uid.
   

2. Difference between @classmethod and @staticmethod: What is the difference between @staticmethod and @classmethod in Python?