Thread: virtual function only works on dynamic declaration? (use of new)

I tried to find an answer on google but no luck..

considering this code...

Code:

#include <iostream>

using namespace std;

class A
{
public:
       A(){}
       virtual void func(){cout<< "I'm A";}
      };

class B : public A
{
public:
       B() : A() {}
       void func(){cout<<"I'm B";}
      };

class XX
{
public:
      A a;
      XX() {}
};

class YY : public XX
{
public:
       YY(){
              a = B();
            }
};

int main()
{
    YY  y = YY();
    y.a.func();  //outputs I'm A
    
    cout<<std::endl;
    A* a = new B();
    a->func();   //outputs I'm B
    delete a;
    
    cout<< std::endl;
    
    A b = B();
    b.func(); //outputs I'm A
    
    system("PAUSE");
    return 0;
}

does virtual function only works on dynamically allocated (objects?)? you cant actually use it on b.func()?

I'm long been working with C++ and yet it still have something that surprises me!

thanks!

Originally Posted by Sebastiani

>> A b = B();

the assignment there doesn't make b a B. it constructs an A object and then assigns it to a temporary B object.

Why?