polymorphism

The process of representing one Form in multiple forms is known as Polymorphism. Here one form represent original form or original method always resides in base class and multiple forms represents overridden method which resides in derived classes.

Polymorphism is derived from 2 greek words: poly and morphs. The word "poly" means many and morphs means forms. So polymorphism means many forms.

Real life example of Polymorphism in C++

Suppose if you are in class room that time you behave like a student, when you are in market at that time you behave like a customer, when you at your home at that time you behave like a son or daughter, Here one person have different-different behaviors.

Type of polymorphism

• Compile time polymorphism
• Run time polymorphism

Compile time polymorphism

In C++ programming you can achieve compile time polymorphism in two way, which is given below;

• Method overloading
• Method overriding

Method Overloading in C++

Whenever same method name is exiting multiple times in the same class with different number of parameter or different order of parameters or different types of parameters is known as method overloading. In below example method "sum()" is present in Addition class with same name but with different signature or arguments.

Example of Method Overloading in C++

#include<iostream.h>
#include<conio.h>

class Addition
{
public:
void sum(int a, int b)
{
cout<<a+b;
}
void sum(int a, int b, int c)
{
cout<<a+b+c;
}
};
void main()
{
clrscr();
Addition obj;
obj.sum(10, 20);
cout<<endl;
obj.sum(10, 20, 30);
}

Output

30
60

Method Overriding in C++

Define any method in both base class and derived class with same name, same parameters or signature, this concept is known as method overriding. In below example same method "show()" is present in both base and derived class with same name and signature.

Example of Method Overriding in C++

#include<iostream.h>
#include<conio.h>

class Base
{
 public:
 void show()
 {
  cout<<"Base class";
 }
};
class Derived:public Base
{
 public:
 void show()
 {
  cout<<"Derived Class";
 }
}

int mian()
{
 Base b;       //Base class object
 Derived d;  //Derived class object
 b.show();    //Early Binding Ocuurs
 d.show();   
getch();
}

Output

Base class
Derived Class

Run time polymorphism

In C++ Run time polymorphism can be achieve by using virtual function.

A virtual function is a member function of class that is declared within a base class and re-defined in derived class.

When you want to use same function name in both the base and derived class, then the function in base class is declared as virtual by using the virtual keyword and again re-defined this function in derived class without using virtual keyword.

Syntax

 
virtual return_type function_name()
{
 .......
 .......
}

Virtual Function Example

 
#include<iostream.h>
#include<conio.h>

class A
{
public:
 virtual void show()
 {
  cout<<"Hello base class";
 }
};

class B : public A
{
 public:
  void show()
  {
   cout<<"Hello derive class";
 }
};

void main()
{
clrsct();
A aobj;
B bobj;
A *bptr;
bptr=&aobj;
bptr->show();  // call base class function

bptr=&bobj;
bptr->show();  // call derive class function
getch();
}

Output

 
Hello base class
Hello derive class