它是否适用于在同一个应用程序中使用django信号

Question

尝试以最干净的方式向我的应用添加电子邮件通知.当模型的某些字段发生变化时,应该向用户发送通知.这是我的旧解决方案:

from django.contrib.auth import User

class MyModel(models.Model):
    user = models.ForeignKey(User)
    field_a = models.CharField()
    field_b = models.CharField()

    def save(self, *args, **kwargs):
        old = self.__class__.objects.get(pk=self.pk) if self.pk else None
        super(MyModel, self).save(*args, **kwargs)
        if old and old.field_b != self.field_b:
            self.notify("b-changed")
        # Sevelar more events here
        # ...

    def notify(self, event)
        subj, text = self._prepare_notification(event)
        send_mail(subj, body, settings.DEFAULT_FROM_EMAIL, [self.user.email], fail_silently=True)

这个工作正常,而我有一两种通知类型,但之后我觉得在我的save()方法中有这么多代码感觉不对.所以,我将代码更改为基于信号:

from django.db.models import signals

def remember_old(sender, instance, **kwargs):
    """pre_save hanlder to save clean copy of original record into `old` attribute
    """
    instance.old = None
    if instance.pk:
        try:
            instance.old = sender.objects.get(pk=instance.pk)
        except ObjectDoesNotExist:
            pass

def on_mymodel_save(sender, instance, created, **kwargs):
    old = instance.old
    if old and old.field_b != instance.field_b:
        self.notify("b-changed")
    # Sevelar more events here
    # ...

signals.pre_save.connect(remember_old, sender=MyModel, dispatch_uid="mymodel-remember-old")
signals.post_save.connect(on_mymodel_save, sender=MyModel, dispatch_uid="mymodel-on-save")

好处是我可以将事件处理程序分成不同的模块,减小大小,models.py我可以单独启用/禁用它们.缺点是这个解决方案是更多的代码和信号处理程序与模型本身分开,不知情的读者可以完全错过它们.所以,同事们,你觉得它值得吗？

Answer 1

我认为这是个好主意。最近 DjangoCon 上的“非耦合设计的自定义信号”演讲是有关 Django 中信号的可能性和适用性的重要资源。