观察者模式
最近考试有考过几次,便仔细瞧瞧了这是何物。
我理解其中核心的点就在于,当一个观察者观察到发生了改变,不仅他自身要进行更新,其余所有的观察者都将被通知到并进行更新。
代码实现如下:
from abc import ABCMeta, abstractmethod class Subject(object): def __init__(self): self.observers = [] self._state = "" @property def state(self): return self._state @state.setter def state(self, value): self._state = value self.notify_all() def add_observers(self, observer): self.observers.append(observer) def notify_all(self): for observer in self.observers: observer.update(self.state) class Observer(metaclass=ABCMeta): def __init__(self, subject): subject.add_observers(self) @abstractmethod def update(self, state): """all observers must implement this function to become a observer""" class RainObserver(Observer): def __init__(self, subject): super().__init__(subject) def update(self, state): print(self.__class__.__name__, "had updated! now state: ", state) class SunObserver(Observer): def __init__(self, subject): super().__init__(subject) def update(self, state): print(self.__class__.__name__, "had updated! now state: ", state) if __name__ == '__main__': tmp_subject = Subject() RainObserver(tmp_subject) SunObserver(tmp_subject) tmp_subject.state = "Rain"
输出:
RainObserver had updated! now state: Rain
SunObserver had updated! now state: Rain
进一寸有进一寸的欢喜。