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# 导入未来模块以支持类型注解
from __future__ import annotations# 导入抽象基类模块和随机数生成器
from abc import ABC, abstractmethod
from random import randrange# 导入列表类型注解
from typing import List# 定义观察者模式中的主体接口
# 导入未来模块以支持类型注解
from __future__ import annotations# 导入抽象基类模块和随机数生成器
from abc import ABC, abstractmethod
from random import randrange# 导入列表类型注解
from typing import List# 定义观察者模式中的主体接口Subject
class Subject(ABC):主体接口声明一组用于管理订阅者的方法。abstractmethoddef attach(self, observer: Observer) - None:将观察者附加到主体。passabstractmethoddef detach(self, observer: Observer) - None:从主体中移除观察者。passabstractmethoddef notify(self) - None:通知所有观察者有关事件的信息。pass# 定义具体主体类ConcreteSubject
class ConcreteSubject(Subject):具体主体拥有对所有订阅者至关重要的状态并在状态变化时通知观察者。_state: int None为了简化起见主体的状态对所有订阅者至关重要存储在此变量中。_observers: List[Observer] []订阅者列表。在实际应用中订阅者列表可以更全面地存储按事件类型分类等。def attach(self, observer: Observer) - None:print(主体已附加一个观察者。)self._observers.append(observer)def detach(self, observer: Observer) - None:self._observers.remove(observer)订阅管理方法。def notify(self) - None:触发每个订阅者的更新。print(主体正在通知观察者...)for observer in self._observers:observer.update(self)def some_business_logic(self) - None:通常订阅逻辑只是主体所能做的工作的一部分。主体通常包含一些重要的业务逻辑当即将发生或已经发生重要事情时触发通知方法。print(\n主体我正在做一些重要的事情。)self._state randrange(0, 10)print(f主体我的状态刚刚变更为{self._state})self.notify()# 定义观察者接口Observer
class Observer(ABC):观察者接口声明由主体使用的update方法。abstractmethoddef update(self, subject: Subject) - None:接收主体的更新。pass# 定义具体观察者类ConcreteObserverA 和 ConcreteObserverB具体观察者对它们所附属的主体发出的更新做出反应。
class ConcreteObserverA(Observer):def update(self, subject: Subject) - None:if subject._state 3:print(具体观察者A对事件作出反应)class ConcreteObserverB(Observer):def update(self, subject: Subject) - None:if subject._state 0 or subject._state 2:print(具体观察者B对事件作出反应)# 客户端代码
if __name__ __main__:subject ConcreteSubject()observer_a ConcreteObserverA()subject.attach(observer_a)observer_b ConcreteObserverB()subject.attach(observer_b)subject.some_business_logic()subject.some_business_logic()subject.detach(observer_a)subject.some_business_logic()输出
Subject: Attached an observer.
Subject: Attached an observer.Subject: Im doing something important.
Subject: My state has just changed to: 0
Subject: Notifying observers...
ConcreteObserverA: Reacted to the event
ConcreteObserverB: Reacted to the eventSubject: Im doing something important.
Subject: My state has just changed to: 5
Subject: Notifying observers...
ConcreteObserverB: Reacted to the eventSubject: Im doing something important.
Subject: My state has just changed to: 0
Subject: Notifying observers...
ConcreteObserverB: Reacted to the event 参考 参考
