C++单例模式

#include "stdafx.h"#include<iostream>using namespace std;class singleton1 //懒汉模式{public:static singleton1 *getInstance(){if(NULL == m_instance1){//Lock(); 可自己实现Lock类，或使用boost库中的if(NULL == m_instance1){m_instance1 = new singleton1();cout<<"singleton1 created!"<<'\n';}//Ulock();}return m_instance1;}static void destoryInstance(){if(NULL != m_instance1){delete m_instance1;m_instance1 = NULL;cout<<"delete singleton1"<<'\n';}}private:static singleton1 * m_instance1;singleton1(){};};singleton1 * singleton1::m_instance1 = NULL; //new singleton1();//懒汉式class singleton2 //饿汉模式{public:static singleton2 *getInstance(){//因为静态初始化在程序开始时，也就是进入主函数之前，由主线程以单线程方式完成了初始化，//所以静态初始化实例保证了线程安全性。static singleton2 instance2; //局部静态变量  cout<<"singleton2 created!"<<'\n';return &instance2;}private:singleton2(){};};class singleton3  //解决懒汉式的内存泄漏问题{public:static singleton3 * getInstance(){if(NULL == m_instance3){//Lock(); 可自己实现Lock类，或使用boost库中的if(NULL == m_instance3){m_instance3 = new singleton3();cout<<"singleton3 created!"<<'\n';}//Ulock();}return m_instance3;}private:singleton3(){}static singleton3 * m_instance3;class Gc{private:~Gc(){if(m_instance3 != NULL){delete m_instance3;m_instance3 = NULL;cout<<"delete m_instance3";}}};static Gc Gc;//定义一个静态成员变量，程序结束时，系统会自动调用它的析构函数  };singleton3 * singleton3::m_instance3 = NULL;int main(){singleton1 * instance1_1 = singleton1::getInstance();singleton1 * instance1_2 = singleton1::getInstance();if(instance1_1 == instance1_2)cout<<"instance1_1 == instance1_2"<<'\n';singleton2 * instance2_1 = singleton2::getInstance();singleton2 * instance2_2 = singleton2::getInstance();if(instance2_1 == instance2_2)cout<<"instance2_1 == instance2_2"<<'\n';singleton3 * instance3_1 = singleton3::getInstance();singleton3 * instance3_2 = singleton3::getInstance();if(instance3_1 == instance3_2)cout<<"instance3_1 == instance3_2"<<'\n';instance1_1->destoryInstance(); //手动delete,instance1_1//instance2_1 在程序结束后会自动析构 //instance3_1 在程序运行结束时，系统会调用singleton3的静态成员Gc的析构函数，该析构函数会进行资源的释放while(1);return 0;}