1、观察者模式
话题订阅模式。观察者模式有两个角色，分别是话题发布者和话题订阅者（即观察者）。发布者就是把消息发送给话题，观察者就是订阅这个话题从而得到最新的资讯。这个模式的作用就拿手机的消息推送来说，app身为观察者提前订阅好话题，一旦发布者把信息发送给话题，所有的观察者就会收到这个信息。
2、观察者模式简单代码
定义发布者
class Subject:def __init__(self):self._observers = []def attach(self, observer):self._observers.append(observer)def detach(self, observer):self._observers.remove(observer)def notify(self,message):for observer in self._observers:observer.update(self, message)
定义观察者
class Observer:def update(self, subject,message):passclass ConcreteObserverA(Observer):def update(self, subject,message):print("ConcreteObserverA: {message}")class ConcreteObserverB(Observer):def update(self, subject,message):print("ConcreteObserverB: {message}")
使用观察者模式
# 创建主题对象
subject = Subject()# 创建观察者对象
observer_a = ConcreteObserverA()
observer_b = ConcreteObserverB()# 注册观察者到主题
subject.attach(observer_a)
subject.attach(observer_b)# 模拟主题状态改变并通知观察者
subject.notify()# 输出:
# ConcreteObserverA: Reacted to the event
# ConcreteObserverB: Reacted to the event
实际案例：和twisted联合运用
from twisted.internet.protocol import ReconnectingClientFactory, Protocol
from twisted.protocols.basic import LineReceiver
from twisted.internet.endpoints import TCP4ClientEndpoint
from twisted.internet import reactor
class Subject:"""定义发布者"""def __init__(self):self._observers = []def attach(self, observer):self._observers.append(observer)def detach(self, observer):self._observers.remove(observer)def notify(self,message):for observer in self._observers:observer.update(self, message)class Observer:"""定义观察者"""def update(self, subject,message):passclass ConcreteObserverA(Observer):"""观察者A"""def update(self, subject,message):print(f"观察到{message}")class ConcreteObserverLog(Observer):def update(self, subject,message):print(f"{message}正在写入日志文件")class ClientProtocol(LineReceiver): "客户端数据接受及处理模块" #根据帧尾巴解决粘包 delimiter = b'\x5F\x5F\x65\x6E\x64\x5F\x5F'def __init__(self):#开一个线程，可以不断接受客户端用户的输入、点击动作之类的，而不影响主线程reactor.callInThread(self.user_input)#初始化发布者，赋值给self.subject，用来发布信息用self.subject.notify(message)self.subject = Subject()#初始化观察者a和观察者bobserver_a = ConcreteObserverA()observer_b = ConcreteObserverLog()#观察者a和观察者b订阅self.subject发布的话题，使用attach订阅self.subject.attach(observer_a)sself.ubject.attach(observer_b)def connectionLost(self, reason):print("Disconnected from the server!") def lineReceived(self, line):#不断地接受服务端的信息；websocket、tcp协议等长连接会一直收到服务器信息#这里通过发布者subject.notify，不断地把新消息发布到话题上，这样每次有新消息#观察者的信息就会更新，并对应动作，比如写入日志文件、打印到终端self.subject.notify(line)def user_input(self):while True:the_input = input("请输入命令（输入'exit'退出）: ")if command_key == 'EXIT':print("正在退出...")self.transport.loseConnection()breakclass ClientFactory(ReconnectingClientFactory):"""Tcp 连接模块"""def startedConnecting(self, connector):print('Started to connect.')def buildProtocol(self, addr):print('Connected.')return ClientProtocol()def clientConnectionLost(self, connector, reason):print('Lost connection. Reason:', reason)def clientConnectionFailed(self, connector, reason):print('Connection failed. Reason:', reason)ReconnectingClientFactory.clientConnectionFailed(self, connector, reason)
#运行起来twisted
ClientInput = ClientFactory()
sender_endpoint = TCP4ClientEndpoint(reactor, "192.168.1.100", 9981)
sender_endpoint.connect(ClientInput)
reactor.run() 
