C++中的回调函数实现，sink方式

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)
    {
        cout << "downloading: " << pURL << "" << 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)
    {
        cout << "OnDownloadFinished, URL:" << pURL << "    status:" << bOK << endl;
    }
};