设计模式学习Chain Of Responsiblity（责任链）

意图:使多个对象都有机会处理请求，从而避免请求的发送者和接收者之间的耦合关系.将这些对象连成一条链，并沿着这条链传递请求，直到一个对象处理它为止.

适用性：

有多个对象可以处理一个请求，那个对象处理该请求运行时自动确定

你想在不明确制定接受者的情况下，向多个对象中的一个提交一个请求

可处理一个请求的对象集合应被动态指定

示例图:

示例代码:

class CHandler
{
public:
    CHandler(CHandler* nextHandler);
public:
    ~CHandler(void);
    public:
    void HandleRequest(CRequest req)
    {
        if(IsMatch(req.GetRequestType()))
        {
            _HandleRequest(req);
        }
        else
        {
            if(m_NextHandler)
            {
                m_NextHandler->HandleRequest(req);
            }
            else
            {
                _tprintf(_T("unhandler message/n"));
            }                       
        }
    }
protected:
    virtual void _HandleRequest(CRequest req) =0;
    virtual bool IsMatch(CRequest::RequestType reqType)=0;
private:
    CHandler* m_NextHandler;
};

//消息处理类处理消息
class CMessageHandler:public  CHandler
{
public:
    CMessageHandler(CHandler* pNextHandler)
    :CHandler(pNextHandler)
    {
   
    }
    public:
    ~CMessageHandler()
    {
    }
    public:
        virtual bool IsMatch(CRequest::RequestType reqType)
    {
        if(reqType == CRequest::eMessage)
        {
            return true;
        }   
        return false;
    }
    virtual void _HandleRequest(CRequest req)
    {
        _tprintf(_T("Message handled/n"));
    }
};

//键盘处理类处理键盘消息
class CKeyHandler:public CMessageHandler
{
public:
    CKeyHandler(CHandler* pNextHandler)
        :CMessageHandler(pNextHandler)
    {

    }
public:
    ~CKeyHandler()
    {
    }
public:
    virtual bool IsMatch(CRequest::RequestType reqType)
    {
        if(reqType == CRequest::eKey)
        {
            return true;
        }   
        return false;
    }
    virtual void _HandleRequest(CRequest req)
    {
        _tprintf(_T("Key Message handled/n"));
    }
};

//处理请求

class CRequest
{
public:
    enum RequestType
    {
        eMessage,
        eKey,
        eMouse,
    };
public:
    CRequest(CRequest::RequestType reqType);
public:
    ~CRequest(void);
   
    public:
        CRequest::RequestType GetRequestType()
    {
    return m_ReqType;
    }
private:
    CRequest::RequestType m_ReqType;
};

//调用

CKeyHandler keyHandler(NULL);
    CMessageHandler messageHandler(&keyHandler);
    CRequest keyReq(CRequest::eKey);
    CRequest msgReq(CRequest::eMessage);
    CRequest mouseReq(CRequest::eMouse);
    messageHandler.HandleRequest(keyReq);
    messageHandler.HandleRequest(msgReq);
    messageHandler.HandleRequest(mouseReq);

结果