Classes: Virtual Functions

Classes: Virtual Functions

Applies To: C++Builder 1 or higher
Category: C++ Language

Virtual functions are member of a base class that can be overridden in a derived class. They're used when a pointer to an object points to a base class and to a derived class.

To declare a virtual function, simply use the virtual keyword. Virtual functions must be declared in the base class:

class Base {

public:

virtual void Do();

};

void Base::Do() {

cout <<< "Base ";< "Base ";

}

You can override the virtual Do function in the derived class:

class Derived : public Base {

public:

virtual void Do();

};

void Derived::Do() {

cout <<< "Derived ";< "Derived ";

}

Now in your main code you can call the two versions of the Do function:

#include <conio>

#include <iostream>

using namespace std;

// ...

int main()

{

Base *pBase = new Base;

Derived *pDerived = new Derived;

pBase->Do();

pDerived->Do();

delete pBase, pDerived;

getch();

return 0;

}