#include<iostream>
using std::cout;
using std::endl;
class base;
base* x;   //全局指针
class base
{
public:
 base(){
     x=this;  //this指向实际的对象，派生类产生后将指向派生类对象。
 }
    virtual void rprint(){
  cout<<"this point to base"<<endl;
 }
};
int main()
{
 x->rprint();
 return 0;
}
class derive:public base
{
public:
 derive(){}
    void rprint();
};
//全局应用对象
derive d1;

void derive::rprint()
{
 cout<<"this point to derive"<<endl;
}