类型转换规则举例

//不要重新定义继承而来的非虚函数 
#include 
using namespace std;

//基类Base1定义
class Base1 {
      
	public:
	    void display() const {
     
	        cout << "Base1::display()" << endl;
	    }
};
//公有派生类Base2定义
class Base2: public Base1 {
      
	public:
	    void display() const {
     
	        cout << "Base2::display()" << endl;
	    }
};
//公有派生类Derived定义
class Derived: public Base2 {
      
	public:
	    void display() const {
     
	        cout << "Derived::display()" << endl;
	    }
};
//参数为指向基类对象的指针
void fun(Base1 *ptr) {
       
    ptr->display();     //"对象指针->成员名"
}
//主函数
int main() 
{
         
    Base1 base1;    //声明Base1类对象
    Base2 base2;    //声明Base2类对象
    Derived derived;    //声明Derived类对象

    fun(&base1);    //用Base1对象的指针调用fun函数
    fun(&base2);    //用Base2对象的指针调用fun函数
    fun(&derived);  //用Derived对象的指针调用fun函数

    return 0;
}