OSG的智能指针，osg::ref_ptr<>

osg::Referenced类管理引用计数内存块，osg::ref_ptr需要使用以它为基类的其它类作为模板参数。

osg::ref_ptr<>类模板重新实现了一系列C++重载符和成员函数，主要有：

• T* get(): 返回管理的指针, { return _ptr; }
• T& operator*(): 返回间接引用，{ return *_ptr; }
• T* operator->():  { return _ptr; }
• operator=(): 各种赋值
• operator==(), operator!=(), and operator!():
• valid(): { return _ptr!=0; }
• release():

简单示例：

#include 
     
      #include 
      
       #include 
       
        class MonitoringTarget : public osg::Referenced{public:    MonitoringTarget(int id) : _id(id)    {        std::cout << "构造目标 " << _id << std::endl;    }protected:    virtual ~MonitoringTarget()    {        std::cout << "目标销毁 " << _id << std::endl;    }    int _id;};int main(int argc, char *argv[]){    osg::ref_ptr
        
          target = new MonitoringTarget(0);    std::cout << "引用前引用计数为: "        << target->referenceCount() << std::endl;    osg::ref_ptr
         
           anotherTarget = target;    std::cout << "引用后引用计数为: "        << target->referenceCount() << std::endl;    for (unsigned int i = 1; i<5; ++i)    {        osg::ref_ptr
          
            subTarget = new MonitoringTarget(i); }}