Dynamic binding and static

Question

I guess i am having some trouble in understanding dynamic bynding.

Suppose we are having 2 classes:

class a1{ //..
virtual void print() const;
};

class a2:a1{ //...
void print() const override;
};

Why is the following true:

a2 item_son;
a1 &item_father = item_son;
item_father->print();

the print called is the one of the son.

After changing your code a little so it compiles, [cannot reproduce](https://ideone.com/DC4TIF). — George, Feb 18 '18 at 14:05
Do you mean it's actually `a1::print` that is called, instead of `a2::print`? Now is *really* the time to learn how to create a [Minimal, Complete, and Verifiable Example](http://stackoverflow.com/help/mcve). — Some programmer dude, Feb 18 '18 at 14:06
You should read about `public` members and `public` inheritance — Killzone Kid, Feb 18 '18 at 14:17
Yepp. it must. That's how virtual functions work. Remove `virtual` and `override` to get the opposite (so that `item_father.print();` will call `a1::print()`). — Scheff's Cat, Feb 18 '18 at 14:36

score 0 · Accepted Answer · answered Feb 18 '18 at 14:57

Actually, the OP did realize the meaning of virtual overloading vs. non-virtual overloading of functions. However, I got my sample running, hence, I'd like to publish it:

#include <iostream>

class A1 {
  public:
  virtual void print() const
  {
    std::cout << "A1::print() called." << std::endl;
  }
};

class A2: public A1 {
  public:
  void print() const override
  {
    std::cout << "A2::print() called." << std::endl;
  }
};

class B1 {
  public:
  void print() const
  {
    std::cout << "B1::print() called." << std::endl;
  }
};

class B2: public B1 {
  public:
  void print() const
  {
    std::cout << "B2::print() called." << std::endl;
  }
};

using namespace std;

int main(void)
{
  A2 a2;
  cout << "Calling a2.print(): ";
  a2.print();
  A1 &a1 = a2;
  cout << "Calling a1.print(): ";
  a1.print();
  B2 b2;
  cout << "Calling b2.print(): ";
  b2.print();
  B1 &b1 = b2;
  cout << "Calling b1.print(): ";
  b1.print();
  return 0;
}

Output:

Calling a2.print(): A2::print() called.
Calling a1.print(): A2::print() called.
Calling b2.print(): B2::print() called.
Calling b1.print(): B1::print() called.

Life demo on ideone

Dynamic binding and static

1 Answers1