Django信号通过装饰器的模型方法？ [英] Django Signal via Decorator on Model Method?

问题描述

我正在尝试像这些提议的信号装饰器。除了装饰器将装饰的方法与信号（将信号的发送方作为装饰器的参数）连接起来之外，我想在类方法上使用装饰器。

I'm trying to do something like these proposed signal decorators. In addition to having a decorator that connects the decorated method to a signal (with the signal's sender as an argument to the decorator), I would like to use the decorator on class methods.

我想使用这样的装饰器：

I'd like to use the decorator like so:

class ModelA(Model):

    @connect.post_save(ModelB)
    @classmethod
    def observe_model_b_saved(cls, sender, instance, created, **kwargs):
        # do some stuff
        pass

装饰器是：

from django.db.models import signals
def post_save(sender):
    def decorator(view):
        signals.post_save.connect(sender=sender, receiver=view)
        return view
    return decorator

当我这样做时，我得到错误是：

The error I get when I do this is:

File "/Library/Python/2.6/site-packages//lib/python2.6/site-packages/django/dispatch/dispatcher.py", line 78, in connect
AssertionError: Signal receivers must be callable.

我猜问题是 @classmethod 返回一个类方法对象不可调用我真的不明白 classmethod 是如何工作的，但是我从此参考页面，类方法对象在从类中访问之前不会转换为可调用对象，例如， ModelA.observe_model_b_saved 。有没有什么方法我可以同时（1）将我的方法定义为模型的类或实例方法，（2）使用装饰器直接在方法定义上将其连接到信号？谢谢！

I guess the problem is that @classmethod returns a class method object which is not callable. I don't really understand how classmethod works under the hood, but I surmise from this reference page that the class method object is not translated into a callable until it is accessed from the class, e.g., ModelA.observe_model_b_saved. Is there any way that I can both (1) define my method as a class or instance method on a model, and (2) connect it to a signal using a decorator directly on the method definition? Thanks!

推荐答案

您的示例代码不清楚，所以我会问，信号侦听器是否实际上必须是 @classmethod ？即如果您还需要访问该类，那么常规方法会执行（然后使用 self .__ class __ ）？它是否需要一个方法（可以使用一个函数）？

It's not clear from your example code, so I'd be asking if the signal listener actually has to be a @classmethod? I.e. Will a regular method do (and then use self.__class__ if you still need to access the class itself)? Does it need to be a method at all (can you just use a function)?

另一种选择可能是使用第二种方法来收听信号并委托调用 @classmethod ：

Another option might be to use a second method to listen to the signal and delegate the call to the @classmethod:

class ModelA(Model): 

    @classmethod 
    def do_observe_model_b_saved(cls, sender, instance, created, **kwargs): 
        # do some stuff 
        pass 

    @connect.post_save(ModelB) 
    def observe_model_b_saved(self, sender, instance, created, **kwargs): 
        self.do_observe_model_b_saved(sender, instance, created, **kwargs)

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