Introduction Basic Concepts of Oops: Encapsulation and
inheritance
these are the basic concepts of Object Oriented Programming. I
wrote it for those who don't have basic concepts of oop, and for those who
feels programming a big monster. I tried to make them understand as much
easiest.
Introduction
In this article i would like to describe the people what are the
basic concepts of Object Oriented Programming The OOP stands on the following
three pillars.
- Object
&Class (Encapsulation)
- Inheritance
- Polymorphism
1 Object & Class (Encapsulation):
Object:
The Object is an Instance in programming language which is made by
inspiring from the real world which contains some properties and methods.
Lets take an example of a person(object) from the real world.
A person is an object, as i told you before that an object could have methodes(behaviour)& properties so here person(object) could have someproperties like his black hair,fair color,tall,and so on..Simillarly it could have themethodes like Eat,Run,Play,Sleep and so on..All these properties & methodes are kept stored in a seperate class.
Class:
A class is basically a container where object lies..In programming
we define all the properties&methodes in a seperate class while we make
object of that class in main class... It means we generate the objects from
main class, lets have a look..
class cat
{
public void eat()
{
console.writeline("cat eats mouse");
}
public void walk()
{
console.writeline("It walks slowly...");
}
}
Here we have defined a class and in 'class
cat' " public void eat() " and " public void walk() "
are methods.now we make an object in main class and call these methods...
static void main ()
{
cat mycat = new
cat();
mycat.eat();
mycat.walk();
console.readline();
}
This is the main
class in which we make an object named mycat of the
classs cat.. after making the cat's class object we can call its methods&properties
by writting "mycat."
when we put dot after the object it calls all the methodes & properties
from the related class...
Encapsulation in OOP?
Encapsulation is the word
which came from the word "CAPSULE" which to put some thing in a kind
of shell. In OOP we are capsuling our code not in a shell but in
"Objects" & "Classes". So it means to hide the
information into objects and classes is called Encapsulation.
2 Inheritance:
The Inheritance is one of the main concepts of oop.Inheritance is
just to adobe the functionality (methods & properties) of one class to
another. This simple term is known as Inheritance.
Lets have a look of code
public class cat
{
public void eat()
{
console.writeline("cat can eat");
}
public void walk()
{
console.writeline("cat can walk");
}
{
public void eat()
{
console.writeline("cat can eat");
}
public void walk()
{
console.writeline("cat can walk");
}
}
now we make another class of another cat and we inherit the
methods of the first class to the new class.Do remember in programming we
inherit one class to another by coding " : " colon between the parent
and child class.
Lets have a look..
public class EgyptianCat : cat
{
public void jump()
{
console.writeline("Egyptian cat can jump");
}
{
public void jump()
{
console.writeline("Egyptian cat can jump");
}
public void bite()
{
console.writeline("Egyptian cat can not bite");
}
}
{
console.writeline("Egyptian cat can not bite");
}
}
static void main()
{
cat
mycat=new cat();
mycat.eat();
mycat.walk();
EgyptianCat
yourcat=new EgyptianCat();
yourcat.eat();
yourcat.walk();
yourcat.jump();
yourcat.bite();
console.readline();
}
this is the code in main class in which we
are inheriting the class EgyptianCat to the class cat, so that the new class
becomes the child class of the first class which is now called the parent
class.
Polymorphism
The word Polymorphism means of many forms.In programming this word
is meant to reuse the single code multiple times. In object oriented
programming its a big question that why the Polymorphism is done, what is the
purpose of it in our code?
There are lots of people who don't even know the purpose and usage
of Polymorphism.Polymorphism is the 3rd main pillar of OOP without it the
object oriented programming is incomplete. Lets go in the depth of
Polymorphism.
Why Polymorphism is done in OOP?
Its obvious that when we do inheritance between two classes, all the methods and properties of the first class are derived to the other class so that this becomes the child class which adobes all the functionality of base class.It can also possesses its own separate methods.
But there is a big problem in inheriting the second class to the first class as it adobes all the methods same as the base class has,which means that after inheritance both(base class& child class) have the methods of same name and same body as shown in this example:~
____Base
Class___
public class fish
{
public void eat()
{
console.writeline("fish eat");
}
public void swim()
{
console.writeline("fish swim");
}
}
{
public void eat()
{
console.writeline("fish eat");
}
public void swim()
{
console.writeline("fish swim");
}
}
______Derived
Class______
class Dolphen:fish
{
public void eat()
{
console.writeline("fish eat");
}
public void swim()
{
console.writeline("fish swim");
}
}
In this example it is clear that when we Inherit two classes, all
the methods with the same name and same body are adobed by the derived class as
shown above.Both methods have the same name but if we change the body of the
second method then it makes Compiler disturb whether to compile base class
method or derived class's
method first...
method first...
Lets have a look of this code..
____Base
Class___
public class fish
{
public void eat()
{
console.writeline("fish eat");
}
public void swim()
{
console.writeline("fish swim");
}
}
______Derived
Class______
class Dolphin:fish
{
public void eat()
{
console.writeline("Dolphin can eat");
}
public void swim()
{
console.writeline("Dolphin can swim");
}
}
In this example we have changed the body of the methods of Derived
class.Now this will make the Compiler disturb to compile which method
first,because they both have same name but different bodies.
To remove this problem and to tell the compiler that which method
is to be executed we need to use Polymorphism.
How the Polymorphism is done?
Polymorphism is used to remove the problem which is shown in the above code.It is done not by changing the name of the methods of both base & derived class.Infect it is done by adding the "virtual" keyword before the base class method, and the "override" keyword before the derived class method.As shown in this exmple:
____Base
Class___
public class fish
{
public
virtual void eat()
{
Console.WriteLine("fish eat");
}
public
virtual void swim()
{
Console.WriteLine("fish swim");
}
}
______Derived
Class______
class Dolphin : fish
{
public
override void eat()
{
Console.WriteLine("Dolphin can eat");
}
public
override void swim()
{
Console.WriteLine("Dolphin can swim");
}
}
This is actually the Polymorphism in which we write virtual
keyword with the base class method and we write override keyword with the
derived class method as we did. It helps the compiler to select the method to
be executed.
Here is the complete code in which Polymorphism has been applied.
class Program
{
public class
fish
{
public
virtual void eat()
{ }
public
virtual void swim()
{ }
public
virtual void dive()
{}
}
public class
Dolphin : fish
{
public
override void eat()
{
Console.WriteLine("Dolphin eats Plants"); }
public
override void swim()
{
Console.WriteLine("Dolphin swims quickly"); }
public
override void dive()
{
Console.WriteLine("Dolphin dive deeply "); }
public void
dance()
{
Console.WriteLine("Dolphin can Dance"); }
}
public class
Shark : fish
{
public
override void eat()
{
Console.WriteLine("Shark eats dead animal"); }
public
override void swim()
{
Console.WriteLine("Sharks swim fastest than Dolphin"); }
public
override void dive()
{
Console.WriteLine("Sharks Dive deeper than Dolphin"); }
public
void kill()
{
Console.WriteLine("Shark kills Others"); }
}
static void
Main(string[] args)
{
Dolphin D
= new Dolphin();
D.dance();
D.dive();
D.eat();
D.swim();
Shark S =
new Shark();
S.kill();
S.dive();
S.eat();
S.swim();
Console.ReadLine();
}
}
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