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