职责链模式

#include <iostream>
using namespace std;

#define REQUEST1 1
#define REQUEST2 2
#define REQUEST3 3

/* ***********************************************************************
 * 职责链模式
 * 将请求传递到可以处理的类为止，子类中包含着处理的下一个对象指针
 * 默认处理程序终结处理
 * 在每个处理类中判定请求是不是可以处理，并且可以做一次预处理
 * ***********************************************************************/


typedef struct _request {
    int nType;
}Request;

class Handler;

class Handler {
public:
    virtual void SetHandler(Handler* pHandler) = 0;
    virtual int  JudgeRequest(Request* pRequest) = 0;
    virtual int  HandleRequest(Request* pRequest) = 0;

protected:
    Handler* m_pHandler;
};

class Handler_1 : public Handler {
public:
    Handler_1() { }
    ~Handler_1() { }

    void SetHandler(Handler* pHandler) {
        m_pHandler = pHandler;
    }

    int JudgeRequest(Request* pRequest) {
        if (pRequest->nType == REQUEST1)
            return 1;
        return 0;
    }

    int HandleRequest(Request* pRequest) {
        if (JudgeRequest(pRequest) > 0) {
            printf("Handler_1\n");
            return 0;
        }
        else {
            m_pHandler->HandleRequest(pRequest);
            return 1;
        }
    }
};

class Handler_2 : public Handler {
public:
    Handler_2() { }
    ~Handler_2() { }

    void SetHandler(Handler* pHandler) {
        m_pHandler = pHandler;
    }

    int JudgeRequest(Request* pRequest) {
        if (pRequest->nType == REQUEST2)
            return 1;
        return 0;
    }

    int HandleRequest(Request* pRequest) {
        if (JudgeRequest(pRequest) > 0) {
            printf("Handler_2\n");
            return 0;
        }
        else {
            m_pHandler->HandleRequest(pRequest);
            return 1;
        }
    }
};

class Handler_3 : public Handler {
public:
    Handler_3() { }
    ~Handler_3() { }

    void SetHandler(Handler* pHandler) {
        m_pHandler = pHandler;
    }

    int JudgeRequest(Request* pRequest) {
        if (pRequest->nType == REQUEST3)
            return 1;
        return 0;
    }

    int HandleRequest(Request* pRequest) {
        if (JudgeRequest(pRequest) > 0) {
            printf("Handler_3\n");
            return 0;
        }
        else {
            m_pHandler->HandleRequest(pRequest);
            return 1;
        }
    }
};

void main()
{
    Handler_1 h1;
    Handler_2 h2;
    Handler_3 h3;

    h1.SetHandler(&h2);
    h2.SetHandler(&h3);


    Request r1;
    r1.nType = REQUEST1;
    h1.HandleRequest(&r1);

    Request r2;
    r2.nType = REQUEST2;
    h1.HandleRequest(&r2);

    Request r3;
    r3.nType = REQUEST3;
    h1.HandleRequest(&r3);
}