作用:
使多個對象都有機(jī)會處理請求,從而避免請求的發(fā)送者和接收者之間的耦合關(guān)系.將這些對象連成一條鏈，并沿著這條鏈傳遞該請求,直到有一個對象處理它為止.
UML結(jié)構(gòu)圖:
抽象基類:
1)Handler:定義一個處理請求的接口,在圖中這個接口就是HandleRequset函數(shù),這個類同時有一個指向Handler對象的指針,指向后續(xù)的處理請求的對象(如果有的話).
解析:
這個模式把可以處理一個請求的對象以鏈的形式連在了一起,讓這些對象都有處理請求的機(jī)會.好比原來看古裝電視中經(jīng)常看到皇宮中召見某人的時候,太監(jiān)們(可以處理一個請求的對象)就會依次的喊:傳XX...這樣一直下去直到找到這個人為止.ChainOfResponsibility模式也是這樣的處理請求的,如果有后續(xù)的對象可以處理,那么傳給后續(xù)的對象處理,否則就自己處理請求.這樣的設(shè)計把請求的發(fā)送者和請求這種的處理者解耦了,好比發(fā)號的皇帝不知道到底是哪個太監(jiān)最后會找到他要找到的人一般,只管發(fā)出命令就OK了.
實(shí)現(xiàn):
1)ChainOfResponsibility.h
/**//********************************************************************
????created:????2006/07/20
????filename:?????ChainOfResponsibility.h
????author:????????李創(chuàng)
????????????????http://www.shnenglu.com/converse/
????purpose:????ChainOfResponsibility模式的演示代碼
*********************************************************************/
#ifndef?CHAINOFRESPONSIBILITY_H
#define?CHAINOFRESPONSIBILITY_H
#include?<stdio.h>
//?抽象基類,定義一個處理請求的接口
class?Handler
{
public:
????Handler(Handler?*pSuccessor?=?NULL);
????virtual?~Handler();
????//?純虛函數(shù),由派生類實(shí)現(xiàn)
????virtual?void?HandleRequset()?=?0;
protected:
????Handler*?m_pSuccessor;
};
class?ConcreateHandler1
????:?public?Handler
{
public:
????ConcreateHandler1(Handler?*pSuccessor?=?NULL)?:?Handler(pSuccessor){}
????virtual?~ConcreateHandler1(){}
????virtual?void?HandleRequset();
};
class?ConcreateHandler2
????:?public?Handler
{
public:
????ConcreateHandler2(Handler?*pSuccessor?=?NULL)?:?Handler(pSuccessor){}
????virtual?~ConcreateHandler2(){}
????virtual?void?HandleRequset();
};
#endif
2)ChainOfResponsibility.cpp
/**//********************************************************************
????created:????2006/07/20
????filename:?????ChainOfResponsibility.cpp
????author:????????李創(chuàng)
????????????????http://www.shnenglu.com/converse/
????purpose:????ChainOfResponsibility模式的演示代碼
*********************************************************************/
#include?"ChainOfResponsibility.h"
#include?<iostream>
Handler::Handler(Handler?*pSuccessor?/**//*?=?NULL*/)?
????:?m_pSuccessor(pSuccessor)
{
}
Handler::~Handler()
{
????delete?m_pSuccessor;
????m_pSuccessor?=?NULL;
}
void?ConcreateHandler1::HandleRequset()
{
????if?(NULL?!=?m_pSuccessor)
????{
????????m_pSuccessor->HandleRequset();
????}
????else
????{
????????std::cout?<<?"HandleRequset?by?ConcreateHandler1\n";
????}
}
void?ConcreateHandler2::HandleRequset()
{
????if?(NULL?!=?m_pSuccessor)
????{
????????m_pSuccessor->HandleRequset();
????}
????else
????{
????????std::cout?<<?"HandleRequset?by?ConcreateHandler2\n";
????}
}
3)Main.cpp
/**//********************************************************************
????created:????2006/07/20
????filename:?????Main.cpp
????author:????????李創(chuàng)
????????????????http://www.shnenglu.com/converse/
????purpose:????ChainOfResponsibility模式的測試代碼
*********************************************************************/
#include?"ChainOfResponsibility.h"
#include?<stdlib.h>
int?main()
{
????Handler?*p1?=?new?ConcreateHandler1();
????Handler?*p2?=?new?ConcreateHandler2(p1);
????p2->HandleRequset();
????delete?p2;
????system("pause");
????return?0;
}