Chain of Responsibility Pattern

1.Chain of Responsibility模式:将可能处理一个请求的对象链接成一个链，并将请求在这个链上传递，直到有对象处理该请求（可能需要提供一个默认处理所有请求的类，例如MFC中的CwinApp类）。

2.Chain of Responsibility Pattern 结构图

3.实现

 #ifndef _HANDLE_H_
 #define _HANDLE_H_

 class Handle
 {
 public:
     virtual ~Handle();
     virtual void HandleRequest() = ;
     void SetSuccessor(Handle* succ);
     Handle* GetSuccessor();

 protected:
     Handle();
     Handle(Handle* succ);

 private:
     Handle* _succ;
 };

 class ConcreteHandleA:public Handle
 {
 public:
     ConcreteHandleA();
     ~ConcreteHandleA();
     ConcreteHandleA(Handle* succ);
     void HandleRequest();

 protected:
 private:
 };

 class ConcreteHandleB:public Handle
 {
 public:
     ConcreteHandleB();
     ~ConcreteHandleB();
     ConcreteHandleB(Handle* succ);
     void HandleRequest();
 protected:
 private:
 };

 #endif

Handle.h

 #include "Handle.h"
 #include <iostream>
 using namespace std;

 Handle::Handle()
 {
     _succ = ;
 }
 Handle::~Handle()
 {
     delete _succ;
 }
 Handle::Handle(Handle* succ)
 {
     this->_succ = succ;
 }
 void Handle::SetSuccessor(Handle* succ)
 {
     _succ = succ;
 }
 Handle* Handle::GetSuccessor()
 {
     return _succ;
 }
 void Handle::HandleRequest()
 {

 }
 ConcreteHandleA::ConcreteHandleA()
 {

 }
 ConcreteHandleA::ConcreteHandleA(Handle* succ):Handle(succ)
 {

 }
 ConcreteHandleA::~ConcreteHandleA()
 {

 }
 void ConcreteHandleA::HandleRequest()
 {
     if (this->GetSuccessor() != )
     {
         cout<<"ConcreteHandleA 我把处理权给后继节点....."<<endl;
         this->GetSuccessor()->HandleRequest();
     }
     else
     {
         cout<<"ConcreteHandleA 没有后继了，我必须自己处理...."<<endl;
     }
 }
 ConcreteHandleB::ConcreteHandleB()
 {

 }
 ConcreteHandleB::ConcreteHandleB(Handle* succ):Handle(succ)
 {

 }
 ConcreteHandleB::~ConcreteHandleB()
 {

 }
 void ConcreteHandleB::HandleRequest()
 {
     if (this->GetSuccessor() != )
     {
         cout<<"ConcreteHandleB 我把处理权给后继节点....."<<endl;
         this->GetSuccessor()->HandleRequest();
     }
     else
     {
         cout<<"ConcreteHandleB 没有后继了，我必须自己处理...."<<endl;
     }
 }

Handle.cpp

 #include "Handle.h"
 #include <iostream>
 using namespace std;

 int main(int argc,char* argv[])
 {
     Handle* h1 = new ConcreteHandleA();
     Handle* h2 = new ConcreteHandleB();
     h1->SetSuccessor(h2);
     h1->HandleRequest();
     return ;
 }

main.cpp