Chain of Responsibility模式

Chain of Responsibility模式

    熟悉MFC的朋友都知道，MFC是"基于消息，事件驱动"滴，它的向上传递消息的机制跟职责链的思想是相同的，其实Qt中的

touchEvent也是这样处理的。

    职责链模式的最大一个优点就是降低了系统的耦合性，请求的发送者完全不知道该请求会被哪个应答对象处理。

C++代码示例：

<strong>//Handle.h</strong>#ifndef _HANDLE_H_#define _HANDLE_H_class Handle{    public:    virtual ~Handle();    virtual void HandleRequest() = 0;    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();};class ConcreteHandleB:public Handle{public:    ConcreteHandleB();    ~ConcreteHandleB();    ConcreteHandleB(Handle* succ);    void HandleRequest();};#endif //~_HANDLE_H_

<strong>//Handle.cpp</strong>#include "Handle.h"#include <iostream>using namespace std;Handle::Handle(){    _succ = 0;}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() != 0)    {        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() != 0)    {        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;    }}

<strong>//main.cpp</strong>#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 0;}