多态性7

#include<iostream>
using namespace std;
class Base{
public:
virtual void fun1() {
cout <<"Base::fun1()"<<endl;
}
virtual ~Base() {}
};
class Derived1:public Base{
public:
virtual void fun1() {
cout <<"Derived1::fun1()"<<endl;
}
virtual void fun2() {
cout <<"Derived1::fun2()"<<endl;
}
};
class Derived2:public Derived1{
public:
virtual void fun1() {
cout <<"Derived2::fun1()"<<endl;
}
virtual void fun2() {
cout <<"Derived2::fun2()"<<endl;
}
};
void fun(Base *b){
b->fun1();
Derived1 *d=dynamic_cast<Derived1 *>(b);
if(d!=0) d->fun2();
}
int main()
{
Base b;
fun(&b);
Derived1 d1;
fun(&d1);
Derived2 d2;
fun(&d2);
return 0;
}