引用类型实现的单件模式

// 单件模式#include <iostream>#include <new>using namespace std;// Singletonclass Singleton{public:static Singleton& instance(){return m_S;}int GetValue(){return m_I;}void SetValue(int i){m_I = i;}private:static Singleton m_S;int m_I;Singleton() : m_I(0){}Singleton(int i) : m_I(i){}Singleton(const Singleton&); // disallowedSingleton& operator = (const Singleton&); // disallowed};Singleton Singleton::m_S(49);int main(){Singleton& s = Singleton::instance();cout << s.GetValue() << endl;Singleton& s2 = Singleton::instance();s2.SetValue(0);cout << s.GetValue() << endl;return 0;}