意图:
使多个对象都有机会处理请求,从而避免请求的发送者和接收者之间的耦合关系。将这些对象连成一条链,并沿着这条链传递该请求,直到有一个对象处理它为止。
适用性:
有多个的对象可以处理一个请求,哪个对象处理该请求运行时刻自动确定。
你想在不明确指定接收者的情况下,向多个对象中的一个提交一个请求。
可处理一个请求的对象集合应被动态指定。
#!/usr/bin/python #coding:utf8 """ Chain """ class Handler: def successor(self, successor): self.successor = successor class ConcreteHandler1(Handler): def handle(self, request): if request > 0 and request <= 10: print("in handler1") else: self.successor.handle(request) class ConcreteHandler2(Handler): def handle(self, request): if request > 10 and request <= 20: print("in handler2") else: self.successor.handle(request) class ConcreteHandler3(Handler): def handle(self, request): if request > 20 and request <= 30: print("in handler3") else: print('end of chain, no handler for {}'.format(request)) class Client: def __init__(self): h1 = ConcreteHandler1() h2 = ConcreteHandler2() h3 = ConcreteHandler3() h1.successor(h2) h2.successor(h3) requests = [2, 5, 14, 22, 18, 3, 35, 27, 20] for request in requests: h1.handle(request) if __name__ == "__main__": client = Client()