C++ 单例模式 demo

//单例模式


/*
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,单例对象持有对自己的引用;
*/

#include "string.h"#include "iostream.h"class SingletonClass{private:static SingletonClass instance;char Classname[30];SingletonClass(){cout<<"!!!!!"<<endl;//调用构造函数的标记strcpy(Classname, "SingletonClass");}SingletonClass(SingletonClass &instance){cout<<"~~~~~~~~"<<endl;//调用拷贝构造函数的标记strcpy(instance.Classname,this->Classname);}public:char *getClassName(){return Classname;}static SingletonClass& getInstance(){return instance;//返回对象时调用拷贝构造函数}void setClassName(char *p){strcpy(Classname, p);}};SingletonClass SingletonClass::instance;int main(int argc, char *argv[]){SingletonClass *p = &SingletonClass::getInstance();//获取实例的指针cout<<"class name:"<<p->getClassName()<<endl;p->setClassName("123456");cout<<"class name:"<<p->getClassName()<<endl;cout<<"--------------------------------------------"<<endl;    SingletonClass *p1 = &SingletonClass::getInstance();//再次获取实例的指针cout<<"class name:"<<p1->getClassName()<<endl;//输出123456cout<<"class name:"<<p->getClassName()<<endl;//如果函数不反回引用，则输出SingletonClass（临时对象）cout<<"--------------------------------------------"<<endl;cout<<"p:"<<p<<"p1:"<<p1<<endl;return 0;}