What is Virtual Function

What is Virtual Function?

A virtual function is a member function within the base class that we redefine in a derived class. It is declared using the virtual keyword. When a class containing virtual function is inherited, the derived class redefines the virtual function to suit its own needs. The compiler performs late binding on this function. To make a function virtual, we write the keyword virtual before the function definition.

#include<iostream.h>

class Animals

{

   public:

   virtual void sound()

   {

     cout << "this is parent class" << endl;

   }

};

class Dogs : public Animals

{

      public:

      void sound()

     {

       cout << "Dogs bark" << endl;

      }

};

int main()

{

   Animals *a;

   Dogs d;

   a= &d;

   a -> sound();

   return 0;

}

Rules for Virtual Function in C++:

• They are always defined in a base class and overridden in derived class but it is not mandatory to override in the derived class.

• The virtual functions must be declared in the public section of the class.

• They cannot be static or friend function also cannot be the virtual function of another class.

• The virtual functions should be accessed using a pointer to achieve run time polymorphism.