发布-订阅模式和注册模式 16/30 | Python 主题月

写在前面

本文正在参加「Python主题月」，详情查看活动链接

这个月是 Python 活动月，我决定尝试用 Python 来刷这 30 天的每日一题和随机一题。然后如果周末有精力，我想捣鼓捣鼓这个python-patterns

设计模式对我来说更多的是学习而不是我的个人经验总结，所以我很可能理解偏，如果有大佬见到了请及时指出，我之所以选择在掘金来写一些个人的东西是因为这里的文章质量更高，我不希望后来者看到了这些文章被误导。

发布-订阅模式

class Provider:
    def __init__(self):
        self.msg_queue = []
        self.subscribers = {}

    def notify(self, msg):
        self.msg_queue.append(msg)

    def subscribe(self, msg, subscriber):
        self.subscribers.setdefault(msg, []).append(subscriber)

    def unsubscribe(self, msg, subscriber):
        self.subscribers[msg].remove(subscriber)

    def update(self):
        for msg in self.msg_queue:
            for sub in self.subscribers.get(msg, []):
                sub.run(msg)
        self.msg_queue = []


class Publisher:
    def __init__(self, msg_center):
        self.provider = msg_center

    def publish(self, msg):
        self.provider.notify(msg)


class Subscriber:
    def __init__(self, name, msg_center):
        self.name = name
        self.provider = msg_center

    def subscribe(self, msg):
        self.provider.subscribe(msg, self)

    def unsubscribe(self, msg):
        self.provider.unsubscribe(msg, self)

    def run(self, msg):
        print(f"{self.name} got {msg}")


def main():
    """
    >>> message_center = Provider()

    >>> fftv = Publisher(message_center)

    >>> jim = Subscriber("jim", message_center)
    >>> jim.subscribe("cartoon")
    >>> jack = Subscriber("jack", message_center)
    >>> jack.subscribe("music")
    >>> gee = Subscriber("gee", message_center)
    >>> gee.subscribe("movie")
    >>> vani = Subscriber("vani", message_center)
    >>> vani.subscribe("movie")
    >>> vani.unsubscribe("movie")

    # Note that no one subscribed to `ads`
    # and that vani changed their mind

    >>> fftv.publish("cartoon")
    >>> fftv.publish("music")
    >>> fftv.publish("ads")
    >>> fftv.publish("movie")
    >>> fftv.publish("cartoon")
    >>> fftv.publish("cartoon")
    >>> fftv.publish("movie")
    >>> fftv.publish("blank")

    >>> message_center.update()
    jim got cartoon
    jack got music
    gee got movie
    jim got cartoon
    jim got cartoon
    gee got movie
    """


if __name__ == "__main__":
    import doctest

    doctest.testmod()

注册模式

class RegistryHolder(type):

    REGISTRY = {}

    def __new__(cls, name, bases, attrs):
        new_cls = type.__new__(cls, name, bases, attrs)
        """
            Here the name of the class is used as key but it could be any class
            parameter.
        """
        cls.REGISTRY[new_cls.__name__] = new_cls
        return new_cls

    @classmethod
    def get_registry(cls):
        return dict(cls.REGISTRY)


class BaseRegisteredClass(metaclass=RegistryHolder):
    """
    Any class that will inherits from BaseRegisteredClass will be included
    inside the dict RegistryHolder.REGISTRY, the key being the name of the
    class and the associated value, the class itself.
    """


def main():
    """
    Before subclassing
    >>> sorted(RegistryHolder.REGISTRY)
    ['BaseRegisteredClass']

    >>> class ClassRegistree(BaseRegisteredClass):
    ...    def __init__(self, *args, **kwargs):
    ...        pass

    After subclassing
    >>> sorted(RegistryHolder.REGISTRY)
    ['BaseRegisteredClass', 'ClassRegistree']
    """


if __name__ == "__main__":
    import doctest

    doctest.testmod(optionflags=doctest.ELLIPSIS)

小结

参考文献

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