设计模式之singleton

#include <iostream>

using std::cout;
using std::endl;

class Singleton{
public:
 static Singleton& getInstance();//返回引用类型，避免产生对象副本，提高效率
 ~Singleton();
private:
 Singleton();
 static Singleton* state;
 static int count;//测试标志,可有可无
};

Singleton* Singleton::state = 0;
int Singleton::count = 0;

Singleton::Singleton()
{
 count++;
 cout<<"构找了第"<<count<<"个实例"<<endl;
}

Singleton& Singleton::getInstance()
{
 if(!state)
  state = new Singleton();
 return *state;
}

Singleton::~Singleton()
{
 if(state) //刚加上去的判断
  delete state;
 state = 0;
}

int main(void)
{

 Singleton test1 = Singleton::getInstance();

 Singleton test2 = Singleton::getInstance();//不进行对象构造

 return 0;
}