c++中的回调

一：设置一个函数指针，在需要使用的时候调用

#include <iostream>

typedef void (__stdcall *DownloadCallback)(const char *pURL,bool OK);

void DownLoadFile(const char *pURL,DownloadCallback callback)
{

    std::cout<<"downloading..."<<pURL<<""<<std::endl;
    callback(pURL,true);
}

void __stdcall onDownloadFinished(const char* pURL,bool bOK)
{
    std::cout<<"onDownloadFinished..."<<pURL<<"   status:"<<bOK<<std::endl;
}

int main()
{
    DownLoadFile("http://wwww.baidu.com",onDownloadFinished);

    system("pause");
    return 0;
}

 

二：Sink的本质是你按照对方要求实现一个C++接口，然后把你实现的接口设置给对方，对方需要触发事件时调用该接口。上面下载文件的需求，如果用Sink实现，代码如下:

#include<iostream>

class IDownloadSink
{
public: 
    virtual void OnDownloadFinished(const char *pURL,bool bOK) = 0;
};

class CMyDownloader
{
public: 
    CMyDownloader (IDownloadSink *pSink)
        :m_pSink(pSink)
    {

    }

    void DownloadFile(const char* pURL)
    {
        std::cout<<"downloading..."<<pURL<<""<<std::endl;
        if(m_pSink!=NULL)
        {
            m_pSink->OnDownloadFinished(pURL,true);
        }
    }

private:
    IDownloadSink *m_pSink;
};


class CMyFile:public IDownloadSink
{
public: 
    void download()
    {
        CMyDownloader downloader(this);
        downloader.DownloadFile("www.baidu.com");
    }

    virtual void OnDownloadFinished(const char *pURL,bool bOK)
    {
        std::cout<<"onDownloadFinished..."<<pURL<<"   status:"<<bOK<<std::endl;
    }
};

void main()
{
    CMyFile *file = new CMyFile();
    file->download();

    system("pause");
}