学步园

001：

回调函数方式：

typedef void (__stdcall *DownloadCallback)(const char* pURL, bool bOK);
void DownloadFile(const char* pURL, DownloadCallback callback)
{
    cout << "downloading: " << pURL << "" << endl;
    callback(pURL, true);
}
void __stdcall OnDownloadFinished(const char* pURL, bool bOK)
{
    cout << "OnDownloadFinished, URL:" << pURL << "    status:" << bOK << endl;
}
DownloadFile("www.baidu.com", OnDownloadFinished);

002-1:

接口方式（虚函数）：

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(const char* pURL)
    {
        CMyDownloader downloader(this);//想使用DownloadFile函数的时候，对方需要回调自己实现的OnDownloadFinished，所以将this传递给对方，自己已经把相应的实现了
        downloader.DownloadFile(pURL);
    }

    virtual void OnDownloadFinished(const char* pURL, bool bOK)
    {
        cout << "OnDownloadFinished, URL:" << pURL << "    status:" << bOK << endl;
    }
};
CMyFile f1;
f1.download("www.baidu.com");

002-2：
虚函数：

class CWorkFlow
{
    void init()
    {
        _a = 0;
        _b = 0;
    }
    int _a;
    int _b;
public:
    void Start()
    {
         //  初始化
         init(); 
         // 调用处理数据
         Handle( _a, _b );
         // 报告结果
         Report( _a);
    }
    virtual void Handle( int &a, int &b ) = 0;
    virtual void Report( int iRet) = 0;
};


class CMain :
    public CWorkFlow
{
public:
    void Handle( int &a, int &b ) 
    {
        a = a + b/2;
    }

    void Report( int iRet)
    {
        printf("iRet = %d/n", iRet);
    }
};
int main()
{
    CMain main;
    main.Start();
}
003：
事件、委托：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace 委托
{
    public delegate void GreetingDelegate(string name);

    //新建的GreetingManager类
    public class GreetingManager
    {
        //在GreetingManager类的内部声明delegate1变量
        public event GreetingDelegate MakeGreet;

        public void GreetPeople(string name)
        {
            if (MakeGreet != null)
            {     //如果有方法注册委托变量
                MakeGreet(name);      //通过委托调用方法
            }
        }
    }

    class Program
    {
        private static void EnglishGreeting(string name)
        {
            Console.WriteLine("Morning, " + name);
        }

        private static void ChineseGreeting(string name)
        {
            Console.WriteLine("早上好, " + name);
        }

        static void Main(string[] args)
        {
            GreetingManager gm = new GreetingManager();
            gm.MakeGreet += EnglishGreeting;
            gm.MakeGreet += ChineseGreeting;

            gm.GreetPeople("Jimmy Zhang");
        }
    }
}