单例模式

/****单例模式要点：
一是某个类只能有一个实例；二是它必须自行创建这个实例；三是它必须自行向整个系统提供这个实例。
***/

#include <iostream>
using namespace std;

class CSingleton
{
    public:
    static CSingleton * GetInstance()
    {
        if(NULL == m_pInstance)
            m_pInstance = new CSingleton();
        return m_pInstance;
    }
    static void Release()   //必须，否则会导致内存泄露
    {
        if(NULL != m_pInstance)
        {
            delete m_pInstance;
            cout<<"this is CSingleton::Release()"<<endl;
            m_pInstance = NULL;
        }
    }

    protected:
        CSingleton()
        {
            cout<<"CSingleton"<<endl;
        };
        static CSingleton * m_pInstance;
};

CSingleton* CSingleton::m_pInstance = NULL;
/***
class CSingleDraw:public CSingleton
{
public:
    static CSingleDraw* GetInstance()
    {
        if(NULL == m_pInstance)
            m_pInstance = new CSingleDraw();
        return (CSingleDraw*)m_pInstance;
    }
protected:
    CSingleDraw()
    {
        cout<<"CSingleDraw"<<endl;
    }
};
***/
int main()
{
   // CSingleDraw* s1 = CSingleDraw::GetInstance();
   // CSingleDraw* s2 = CSingleDraw::GetInstance();
    CSingleton *s1=CSingleton::GetInstance();
    CSingleton *s2=CSingleton::GetInstance();
    s2->Release(); //this is CSingleton::Release()
    s1->Release();
    return 0;
}