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