设计模式-职责链模式

适用情境:根据请求的不同,交由不同的对象处理,请求沿着一条链传递,知道有一个对象处理为止.

// request.h
#ifndef REQUEST_H
#define REQUEST_H

#include <string>

class Request
{
public:
    Request(std::string content, int number);
public:
    std::string m_strContent;
    int m_nNumber;
};

#endif // REQUEST_H

// request.cpp
#include "request.h"

Request::Request(std::string content, int number)
{
    m_strContent = content;
    m_nNumber = number;
}

// handler.h
#ifndef HANDLER_H
#define HANDLER_H

#include <string>
#include "request.h"

class Handler
{
public:
    Handler(std::string name);
    virtual void SetSuccessor(Handler* handler);
    virtual void RequestHandle(Request* request) = 0;
protected:
    Handler* m_handler;
    std::string m_name;
};

#endif // HANDLER_H

// handler.cpp
#include "handler.h"

Handler::Handler(std::__cxx11::string name)
{
    m_name = name;
}

void Handler::SetSuccessor(Handler *handler)
{
    m_handler = handler;
}

// handlera.h
#ifndef HANLDERA_H
#define HANLDERA_H

#include "handler.h"

class HandlerA : public Handler
{
public:
    HandlerA(std::string name);
    virtual void RequestHandle(Request* request);
};

#endif // HANLDERA_H

// handlera.cpp
#include "handlera.h"
#include <iostream>

HandlerA::HandlerA(std::string name) : Handler(name)
{}

void HandlerA::RequestHandle(Request* request)
{
    if(request->m_nNumber >= 0 && request->m_nNumber < 10)
    {
        std::cout << this->m_name << " handle "
                  << request->m_nNumber << " content: "
                  << request->m_strContent << std::endl;
    }
    else
    {
        if(m_handler != NULL)
        {
            m_handler->RequestHandle(request);
        }
    }
}

// handlerb.h
#ifndef HANDLERB_H
#define HANDLERB_H

#include <string>
#include "handler.h"

class HandlerB : public Handler
{
public:
    HandlerB(std::string name);
    virtual void RequestHandle(Request *request);
};

#endif // HANDLERB_H

// handlerb.cpp
#include "handlerb.h"
#include <iostream>

HandlerB::HandlerB(std::__cxx11::string name) : Handler(name)
{}

void HandlerB::RequestHandle(Request *request)
{
    if(request->m_nNumber >= 10 && request->m_nNumber <100)
    {
        std::cout << this->m_name << " handle "
                  << request->m_nNumber << " content: "
                  << request->m_strContent << std::endl;
    }
    else
    {
        std::cout << "no match request handler" << std::endl;
    }
}

客户端:

// main.cpp
#include <iostream>
#include "handler.h"
#include "request.h"
#include "handlera.h"
#include "handlerb.h"

using namespace std;

int main(int argc, char *argv[])
{
    Request* request = new Request("request content", 9);
    Handler* handlera = new HandlerA("handler AAA");
    Handler* handlerb = new HandlerB("handler BBB");
    handlera->SetSuccessor(handlerb);

    handlera->RequestHandle(request);

    request->m_nNumber = 99;
    handlera->RequestHandle(request);

    return 0;
}