设计模式，观察者模式的源码实现，其中包含智能指针的使用-Design pattern, observer pattern in the source implementation, which includes the use of smart pointers

OSG中智能指针的使用。自己写了一个类，用来模仿OSG的智能指针。(The use of intelligent pointer in OSG. I wrote a class that mimics the intelligent pointer of OSG.)