实例解析Python设计模式编程之桥接模式的运用

我们先来看一个例子：

    #encoding=utf-8 
    # 
    #by panda 
    #桥接模式 

    def printInfo(info): 
      print unicode(info, 'utf-8').encode('gbk') 

    #抽象类：手机品牌 
    class HandsetBrand(): 
      soft = None 
      def SetHandsetSoft(self, soft): 
        self.soft = soft 

      def Run(self): 
        pass 

    #具体抽象类：手机品牌1 
    class HandsetBrand1(HandsetBrand): 
      def Run(self): 
        printInfo('手机品牌1:') 
        self.soft.Run() 

    #具体抽象类：手机品牌2 
    class HandsetBrand2(HandsetBrand): 
      def Run(self): 
        printInfo('手机品牌2:') 
        self.soft.Run() 


    #功能类：手机软件 
    class HandsetSoft(): 
      def Run(self): 
        pass 

    #具体功能类：游戏   
    class HandsetGame(HandsetSoft): 
      def Run(self): 
        printInfo('运行手机游戏') 

    #具体功能类：通讯录   
    class HandsetAddressList(HandsetSoft): 
      def Run(self): 
        printInfo('运行手机通信录') 

    def clientUI(): 
      h1 = HandsetBrand1() 
      h1.SetHandsetSoft(HandsetAddressList()) 
      h1.Run() 
      h1.SetHandsetSoft(HandsetGame()) 
      h1.Run() 

      h2 = HandsetBrand2() 
      h2.SetHandsetSoft(HandsetAddressList()) 
      h2.Run() 
      h2.SetHandsetSoft(HandsetGame()) 
      h2.Run()   
      return 

    if __name__ == '__main__': 
      clientUI();

可以总结出类图是这样的：

所以，桥接模式的概念在于将系统抽象部分与它的实现部分分离，使它们可以独立地变化。
由于目标系统存在多个角度的分类，每一种分类都会有多种变化，那么就可以把多角度分离出来，让它们独立变化，减少它们之间的耦合。

下面我们再来看一个实例：

基本原理请参考相关书籍，这里直接给实例

假期旅游 从目的地角度可以分为 上海和大连，从方式角度可以分为跟团和独体

桥接模式把这两种分类连接起来可以进行选择。

类图：

    # -*- coding: utf-8 -*-
    #######################################################
    # 
    # tour.py
    # Python implementation of the Class DaLian
    # Generated by Enterprise Architect
    # Created on:   11-十二月-2012 16:53:52
    # 
    #######################################################

    from __future__ import division
    from __future__ import print_function
    from __future__ import unicode_literals
    from future_builtins import *


    class TravelForm(object):
      """This class defines the interface for implementation classes.
      """
      def __init__(self, form="stay at home"):
        self.form=form
        pass

      def GetForm(self):
        return self.form
        pass
      pass

    class Group(TravelForm):
      """This class implements the Implementor interface and defines its concrete
      implementation.
      """
      def __init__(self, form="by group"):
        super(Group,self).__init__(form)    
        pass
      pass

    class Independent(TravelForm):
      """This class implements the Implementor interface and defines its concrete
      implementation.
      """
      def __init__(self, form="by myself"):
        super(Independent,self).__init__(form)
        pass

    class Destination(object):
      """This class (a) defines the abstraction's interface, and (b) maintains a
      reference to an object of type Implementor.
      """
      m_TravelForm= TravelForm()

      def __init__(self, info):
        self.info=info
        pass

      def GetInfo(self):
        # imp->Operation();
        return print(self.info + " " +self.form.GetForm())
        pass

      def SetForm(self, form):
        self.form=form
        pass

    class DaLian(Destination):
      """This class extends the interface defined by Abstraction.
      """
      def __init__(self, info="Go to DaLian "):
        super(DaLian,self).__init__(info)
        pass

    class ShangHai(Destination):
      """This class extends the interface defined by Abstraction.
      """
      def __init__(self, info="Go to ShangHai"):
        super(ShangHai,self).__init__(info)
        pass
    #客户端
    if(__name__=="__main__"):

      destination=ShangHai()
      destination.SetForm(Group())
      destination.GetInfo()


      destination=DaLian()
      destination.SetForm(Independent())
      destination.GetInfo()

运行结果