POLYMORPHISM
By Muhammad Waris Zargar
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PolyMorphism
◦ It is combination of two word poly (many) and morphism (form).
◦ In object oriented programming polymorphism is the ability of
object of different types to response to function of same name.
◦ The behavior of object can be implemented in run time.
Pointer To Object
Ptr -> member (data member or member function)
New keyword
◦It is used to allocate memory dynamically
◦It is allocate memory according to the type of pointer
◦It returns the address to the pointer
◦Pointer than work and collect data
◦It is used to create simple variable , object , array
Method:
1st
Class name *ptr = new class name (parameter);
2nd
Int *ptr ;
Ptr = new int
Simple Programme
◦ Class student{
◦ Int a;
◦ Void in(){
cin >> a; }
◦ Void show() {
cout << “age :: ” << age;}
◦ };
◦ Int main(){
student *s = new student;
◦ S ->in();
◦ S ->show();
◦}
Array Of Pointer
◦ Class student{int age; string name;
◦ Void in(){
cin >> name;
◦ }
void show() {
cin >> age;
cout << “name ”
<< name
◦ };
◦ Int main(){
char choice;
int I =0;
◦ Student *waris[50];
◦ Do(){
◦ Waris[i] = new student;
◦ Waris->in();
i++;
◦ Cin >> choice;
◦ }while(choice == ‘y’);
◦ }
waris->show();
}
<<
age;}
Pointer And Inheritance
◦If we use only derive class object then it is called derive
class function every time.
◦Obj . input();
◦Obj .show();
◦ This called every time derive class function
Pare
nt
Ptr
obj3
Pointer And Inheritance
◦In this section if we use overriding method and
make an pointer object of parent class and pass
address of derive class is called parent class
function every time.
◦Parent *obj[50] = & obj;
◦Obj -> input();
◦Obj[i] ->show();
◦ This called every time parent class function
Ptr
obj1
Ptr
obj2
Ptr
obj3
Virtual Function
◦ Virtual means that exist in effect but not in reality .
◦ Virtual function are used to implement polymorphism.
◦ In this way user execute completely different function by same
function call.
◦ Keyword virtual used with function in class
◦ Derive *obj[50];
◦ Obj -> input();
◦ Obj[i] ->show();
◦ It called that function whose class object pass.
Ptr
obj1
Ptr
obj2
Ptr
obj3
Early And Late Binding
◦ Early Binding:
◦ It is also called static binding.
◦ Before polymorphism we doing early binding
◦ The early binding occur when every thing required to call function is known at
compile time.
Late Binding:
It is also called dynamic binding.
Compiler does not knwn which function to be called.
The use of virtual function to implement polymorphism is an example late
bibnding.
Example
◦ Class A{ void show( ){ cout << “I am in parent class function A”}
◦ };
◦ Class B : public A{
void show( ){ cout << “I am in derive class function B”} };
◦ Class C: public A{
void show( ){ cout << “I am in derive class function C”} };
◦ Int main(){
◦ A *waris[5];
◦ Int choice;
◦ Cout << “1 for create obj of class A and 2 for B and 3 for C”;
◦ Cin >> choice;
◦ For(int i=0;i<5;i++){
if(choice == 1)
◦ If(choice == 2) {
waris[i] = new B; }
◦ If(choice == 3) {
waris[i] = new C;
◦ }
◦ }
{
waris[i] =new A;
}
}
Pure Virtual Function
◦ A type of virtual function that has no body is called pure virtual function.
How make a pure virtual function ?
 The virtual keyword at the start of function.
The zero at the end of function declation.
Class waris{
Virtual void show() = 0;
}
Abstract Class
◦ If any class has virtual function is called abstract class.
◦ Abstact class cannot use directly means that it has no object.
◦ But we make pointer of that class.
◦ However , a child class can inherit an abstract class and use it by overriding
pure virtual function.
◦ If not use overriding method then next class is also make abstract class.’
Syntax:
class waris{
Virtual void show()=0;
}
Virtual Base Class Or Diamond Problem
Parent
Child1
Child1
Baby
Thanks
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