python设计模式第十九天【职责链模式】

1.应用场景

（1）将一个任务拆分为具有顺序的多个部分，每个类完成相应的部分，并且顺序执行

（2）软件窗口的消息传播

（3）SERVLET容积的过滤器Filter的实现

2.代码实现

#!/usr/bin/env python
#! _*_ coding:UTF-8 _*_

from abc import ABCMeta, abstractmethod

class Handler(object):

    @abstractmethod
    def handle(self):
        '''具体处理方法在子类中实现'''
        pass

    def handleNext(self):
        '''处理下一个'''
        if hasattr(self, "next_handler") and self.next_handler is not None:
            self.next_handler.handle()

    def setNextHanndler(self, next_handler):
        '''设置下一个处理器'''
        self.next_handler = next_handler

class OneHandler(Handler):

    def handle(self):
        print "one handle"
        self.handleNext()

class TwoHandler(Handler):

    def handle(self):
        print "two handle"
        self.handleNext()

class ThreeHandler(Handler):

    def handle(self):
        print "three handle"
        self.handleNext()


if __name__ == "__main__":
    oneHandler = OneHandler()

    twoHandler = TwoHandler()
    threeHandler = ThreeHandler()

    oneHandler.setNextHanndler(twoHandler)
    twoHandler.setNextHanndler(threeHandler)

    oneHandler.handle()

结果：

/Users/liudaoqiang/PycharmProjects/numpy/venv/bin/python /Users/liudaoqiang/Project/python_project/day19_cor/cor_test.py
one handle
two handle
three handle

Process finished with exit code 0