单件模式

#include <cstdlib>
#include <iostream>

using namespace std;
class Singleton
{
  Singleton(){}
  Singleton(Singleton&a);
  Singleton& operator=(const Singleton&);
public:
  ~Singleton(){
    if(pSing != NULL)
      //delete pSing;
      pSing = NULL;
  }
  void Do(){cout<<"我是唯一的"<<endl;}
  static Singleton* pSing;
  static Singleton* Instance()
  {
    if(pSing == NULL)pSing = new Singleton;
    return pSing;
  }
};
Singleton* Singleton::pSing = NULL;
int main(int argc, char *argv[])
{
    Singleton* pSing = Singleton::Instance();
    pSing->Do();
    pSing = Singleton::Instance();
    pSing->Do();
    delete pSing;
    system("PAUSE");
    return EXIT_SUCCESS;
}