3)oop'concepts

8/17/2019 3)OOP'Concepts

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INTRODUCTION:

OOP is a design philosophy. It stands for Object Oriented Programming. Object-

Oriented Programming (OOP ) uses a different set of programming languages than old

procedural programming languages (C, Pascal , etc.). Everything inOOP is grouped as self

sustainable objects. !ence, you gain re-usability by means of four main object-oriented programming concepts.

In order to clearly understand the object orientation, let"s ta#e your $hand % as an

e&ample. 'he $hand % is a class. our body has to objects of type hand, named left hand

and right hand. 'heir main functions are controlled* managed by a set of electrical

signals sent through your shoulders (through an interface). +o the shoulder is an

interface hich your body uses to interact ith your hands. 'he hand is a ell

architected class. 'he hand is being re-used to create the left hand and the right hand by

slightly changing the properties of it.

The object oriented programming ill give the impression very unnatural to a

programmer ith a lot of procedural programming e&perience. In Object Oriented

programming Encapsulation is the first pace. Encapsulation is the procedure of covering

up of data and functions into a single unit (called class). n encapsulated object is often

called an abstract data type. In this article let us see about it in a detailed manner.

What are Objects?

It is a real time entity.

n object can be considered a thing that can perform a set of related activities. 'he

set of activities that the object performs defines the objects behavior. or e&ample, the

hand can grip something or at!dent (object) can give the name or address. In

pure OOP terms an object is an instance of a class

'he above template describe about object t!dent

/lass is composed of three things name, attributes, and operations

Class:

It is a collection of objects.


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'he above template describe about object t!dent

/lass is composed of three things name, attributes, and operations

public class student

0

1

student objstudent2ne student ()3

ccording to the above sample e can say that t!dent object, named objst!dent" has

created out of the student class.

In real orld you ill often find many individual objects all of the same #ind. s an

e&ample, there may be thousands of other bicycles in e&istence, all of the same ma#e

and model. Each bicycle has built from the same blueprint. In object-oriented terms, e

say that the bicycle is an instance of the class of objects #non as bicycles. In the

softare orld, though you may not have reali4ed it, you have already used classes. or

e&ample, the Te#tbo# control, you alays used, is made out of the Te#tbo# class,

hich defines its appearance and capabilities. Each time you drag a Te#tbo# control,

you are actually creating a ne instance of the Te#tbo# class.

$ncaps!lation" Inheritance"Pol%morphism and abstraction are main pillars o&

OOPs. 'hese have been described belo.

N$$D 'OR $NC(PU)(TION:

'he need of encapsulation is to protect or prevent the code (data) from accidental

corruption due to the silly little errors that e are all prone to ma#e. In Object oriented

programming data is treated as a critical element in the program development and data

is pac#ed closely to the functions that operate on it and protects it from accidental

modification from outside functions.

Encapsulation provides a ay to protect data from accidental corruption. 5ather than

defining the data in the form of public, e can declare those fields as private. 'he Private

data are manipulated indirectly by to ays. 6et us see some e&ample programs in /7

to demonstrate Encapsulation by those to methods. 'he first method is using a pair of

conventional accessor and mutator methods. nother one method is using a named

property. 8hatever be the method our aim is to use the data ith out any damage or

change.


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private type member is one that can only be accessed by members ithin the sametype. or e&ample, if the BankAccount class has a private member, only other membersof the BankAccount class can access or call that member.

lthough the default access for type members is private, I prefer to be e&plicit about myintentions hen declaring type members and include the access modifier, rather thanrely on defaults. I thin# it ma#es the code easier to read and ma#es it clear to other

developers hat my true intention is. 6isting 9:-; shos ho to use the private accessmodifier and offers an e&ample of hy you ould ant to use it.

$#:

using +ystem3

class ame

0 get 0 return m=name3 1

set 0 m=name 2 value3 1 11

Its common to encapsulate the state of your type ith properties. In fact, I alays rapmy type state in a property. In 6isting 9:-;, you can see ho the name of the customeris held in the m_name field, but it is rapped (encapsulated) ith

the CustomerName property. et does not support multiple classes Inheritance.+ynta&@ -public class /lass>ame@ +uper/lass>ame0+tatements---------

1Constr!ctors in Inheritence

this

It is a 5eference Object of /urrent /lass. It refers to the Aembers of the /urrent /lass.

base


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It is a 5eference Object of +uper /lass. It refers to the Aembers of the +uper /lassNote: *

'he first call in a /lass is /lass /onstructor'he first call in a Inheritance is +uper /lass /onstructor

What is Pol%morphism?

Polymorphism means same operation may behave differently on different classes.

E&ample of /ompile 'ime Polymorphism@ Aethod Overloading

E&ample of 5un 'ime Polymorphism@ Aethod Overriding

$#ample o& Compile Time Pol%morphism

+ethod O,erloading

- Aethod ith same name but ith different arguments is called method overloading.

- Aethod Overloading forms compile-time polymorphism.- E&ample of Aethod Overloading@

class 9

0

void hello()

0 /onsole.8rite6ine($!ello%)3 1

void hello(string s)

0 /onsole.8rite6ine($!ello 0B1%,s)3 1

1

$#ample o& R!n Time Pol%morphism

+ethod O,erriding

- Aethod overriding occurs hen child class declares a method that has the same type

arguments as a method declared by one of its superclass.

- Aethod overriding forms 5un-time polymorphism.

- >ote@


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static void main()

0

parent objParent 2 ne child()3

objParent.hello()3

1

**Output

!ello from /hild.

(bstractionAbstraction means that you have some class that is more common than others thatextend it. By example, if you have classes Triangle and Rectangle:

class Triangle

{

public double a; public double b;

public double c;

public double Area

{

get { return triangles area !

!

!

class Rectangle

{

public double a;

public double b;

public double Area

{

get { return rectangles area !

!

!

These classes have something in common " they have property called Area plus alsosides #a and b$ but % dont see any reason to ma&e sides abstract. 'ets add also (ircleand )e have no point of sides at all. *o) lets generali+e these classes and lets createone more common class called hape. Also, lets ma&e it abstract class so this classcannot be created separately " it can be created only through extending.

public abstract class hape

{

public double Area#$;

!

And no) lets )rite previous classes so they extend hape class.


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class Triangle : hape

{

public double a;

public double b;

public double c;

public double Area

{

get { return triangles area !

!

!

class Rectangle : hape

{

public double a;

public double b;

public double Area

{

get { return rectangles area !

!

!

o, )hats the )in, you may as&- &ay, not of these classes use hape as their baseclass. o does (ircle. %n the context )here )e don t care about speci/c properties ofob0ect )e can handle all extended ob0ects as hape. By example, lets calculate totalarea of hapes in list.

'ist1hape2 shapes 3 'isthapes#$ 44 contains circles, triangles and rectangles

double area 3 5;

foreach#hape shape in shapes$

area 63 shape.Area;

44 do something useful )ith area here

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