Singleton design pattern often we talk about and many people think that this mode is very simple. Indeed, from the point of view of pure design pattern, it is not complicated, but from the implementation point of view, in fact, very simple, especially in C + + to achieve it.-Singleton design pattern often we talk about and many people think that this mode is very simple. Indeed, from the point of view of pure design pattern, it is not complicated, but from the implementation point of view, in fact, very simple, especially in C++ to achieve it.