问题及代码:
#include <iostream>
using namespace std;
class Base
{
public:
virtual void Who() =0;
};
class FirstDerived:public Base
{
public:
void Who() { cout<<"F"; }
};
class SecondDerived:public Base
{
public:
void Who() { cout<<"S"; }
};
int main()
{
FirstDerived first_obj;
SecondDerived second_obj;
Base &bref=first_obj;
bref.Who();
bref=second_obj;
bref.Who();
Base *bp;
bp=&first_obj;
bp->Who();
bp=&second_obj;
bp->Who();
return 0;
}
预测结果:
FSFS
运行结果:
错误分析:
在bref=second_obj;这个语句中,由于开始用的是引用,现在这里直接赋值给second_obj不会起到预测的作用