Virtual Base Class in C++ with Example

Multiple repetition of the data member can be corrected by changing the derived class into virtual base class. Any base class which is declared using the keyword virtual is called a virtual base class. Virtual base class is useful method to avoid unnecessary repetition of the same data member in the multiple inheritance hierarchies.

When a class is made a virtual base class C++ takes necessary care to section that only one copy of that class inherited, regardless of how many inheritance pass exists between the virtual base class and derived class.

 It is used when multiple path inheritance.

Example:

#include<iostream.h>

#include<conio.h>

class student

               {

                              int id;

                              char name[20];

   public:

void get();

               };

void student::get()

{

               cout<<”Enter Student Info = ”;

               cin>>id>>name;

}

class theory : virtual public student

               {

                              Protected:

                              int english, french, maths;

public:

void getdata();

               };

void theory :: getdata()

{

cout<<”Enter Marks = ”;

cin>>english>>french>>maths;

}

class sports : virtual public student

{

                              protected:

                              int sm;

                              public:

                              void takes();

};

void sports :: takes()

{

cout<<”Enter Sports Marks = ”;

cin>>sm;

};

class result : public theory, public sports

               {

                              float avg;

                              int total;

                              public:

                              void putdata();

               };

void result :: putdata()

{

               total = english+french+maths+sm;

               avg = total/4;

               cout<<”Student Id = “;

               cout<<id;

               cout<<”Student Name = “;

               cout<<name;

               cout<<”Theory Marks of English, French, maths = ”;

               cout<<english<<french<<maths;

               cout<<”Sport Marks = ”

               cout<<sm;

               cout<<”Total = ”;

               cout<<total;

               cout<<”Average = ”;

               cout<<avg          

};

void main()

{

clrscr();

               result rs;

               rs.get();

               rs.getdata();

               rs.takes();

               rs.putdata();

               getch();

}