c++ 设计模式之 单例模式
概念

单例模式是确保一个变量只有一个实例，并提供一个全局的角度进行访问.

#include <iostream>using namespace std;class Singleton{public:static Singleton *getInstance(); private:Singleton(){}static Singleton* instance;};Singleton* Singleton::instance = 0;Singleton* Singleton::getInstance() {if(!instance) {instance = new Singleton();cout << "getInstance(): First instance\n";return instance;}else {cout << "getInstance(): previous instance\n";return instance;}}int main(){Singleton *s1 = Singleton::getInstance();Singleton *s2 = Singleton::getInstance();return 0;}