行为模式观察者模式

• Z时代
• 2024-01-10
• 分类：综合

意图

观察者模式是一种行为设计模式， 允许你定义一种订阅机制，

可在对象事件发生时通知多个 “观察” 该对象的其他对象。

核心: 被观察者与观察者建立一种自动触发的关系.

模式分析

在热水器模型中

被监听者：热水器的温度(会发生变化).

监听者: 不同的水温，不同的监听者会及时的作出反应.

被观察者：

• 添加监听者
• 删除监听者
• 通知监听者.触发观察者的提供接口.

使用场景.

• django 信号机制

2.推模型和拉模型

*推模型: 被观察者向观察者推送.

*拉模型:

#!/usr/bin/env python
from abc import ABCMeta, abstractmethod
class Observer(metaclass=ABCMeta):
    """
    观察者基类:
    """
    @abstractmethod
    def update(self, water_heater):
        """
        订阅更新事件.
        :param water_heater:
        :return:
        """
        print("xxx WaterHeater:{}".format(water_heater))
class Observable(metaclass=ABCMeta):
    """
    被观察者基类:
    """
    def __init__(self):
        self.__observers = []
    def __str__(self):
        return f"observers:{self.__observers}"
    def register(self, observer):
        if not isinstance(observer, Observer):
            raise TypeError("observer must be instance of Observer")
        self.__observers.append(observer)
    def unregister(self, observer):
        self.__observers.remove(observer)
    def notice(self):
        """
        通知订阅者事件发生
        :return:
        """
        for o in self.__observers:
            # if hasattr(o, "update"):
            o.update(self)
class WaterHeater(Observable):
    """
    热水器
    """
    def __init__(self):
        super().__init__()
        self.__temperature = 25
    def __str__(self):
        print(super().__str__())
        return f"cur temperature:{self.__temperature}"
    @property
    def temperature(self):
        return self.__temperature
    @temperature.setter
    def temperature(self, val):
        self.__temperature = val
        print(self)
        self.notice()
class Account(Observable):
    """
    登陆地记录
    """
    def __init__(self):
        super().__init__()
        self.__city_history = list()
    def __str__(self):
        print(super().__str__())
        return f"cur city_history:{self.__city_history}"
    @property
    def city(self):
        return self.__city_history[-1]
    @city.setter
    def city(self, val):
        if val not in self.__city_history:
            self.__city_history.append(val)
            print(self)
            self.notice()
class WashMode(Observer):
    """
    洗澡模式
    """
    def update(self, water_heater: WaterHeater):
        if 50 < water_heater.temperature < 70:
            print("is good time at wash")
        else:
            print("not good time at wash")
class DrinkMode(Observer):
    """
    饮水模式
    """
    def update(self, water_heater: WaterHeater):
        if water_heater.temperature >= 80:
            print("is good time at drink")
        else:
            print("not good time at drink")
class SmsMode(Observer):
    """
    短信通知
    """
    def update(self, account: Account):
        """
        :param account:
        :return:
        """
        print("sms notify ", account.city)
        pass
class EmailMode(Observer):
    """
    邮件通知
    """
    def update(self, account: Account):
        """
        :param account:
        :return:
        """
        print("email notify ", account.city)
def test_water_mode():
    water_heater = WaterHeater()
    wash_observer = WashMode()
    drink_observer = DrinkMode()
    water_heater.register(wash_observer)
    water_heater.register(drink_observer)
    water_heater.temperature = 60
    water_heater.temperature = 100
def test_other_area_login():
    login = Account()
    email = EmailMode()
    sms = SmsMode()
    login.register(email)
    login.register(sms)
    login.city = "北京"
    login.city = "上海"
def main():
    # test_water_mode()
    test_other_area_login()
    pass
if __name__ == "__main__":
    main()

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