Basic Concepts of oop: Abstraction Explained

Zon
Posted by in OOPS category on for Intermediate level | Points: 150 | Views : 31012 red flag
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In this article I'm describing 'Abstraction', one of the main concept of Object Oriented Programming.Abstraction comes after inheritance and polymorphism, so make yourself clear in the first two topics then do work on Abstraction.I have described both of the topics in my previous lectures.
Best of luck!
faizan_ahmed

Abstraction:


The word abstract means a concept or an idea not associated with any specific instance.

In programming we do apply the same meaning of abstraction by making classes those are not associated with any specific instance. The abstraction is done when we need to only inherit from a certain class, but not need to instantiate objects of that class. In such case the base class can be regarded as "Incomplete". Such classes are known as "Abstract Base Class".


Abstract Base Class:


There are some important points about Abstract Base Class :
  1. An Abstract Base class can not be instantiated it means the object of that class can not be created.
  2. Class having abstract keyword and having, abstract keyword with some of its method (not all) is known as Abstract Base Class.
  3. Class having Abstract keyword and having abstract keyword with all of its methods is known as pure Abstract Base Class.
  4. The method of abstract class has no implementation is known as "operation".  It can be defined as abstract void method ();
  5. An abstract class holds the methods but the actual implementation of those methods is made in derived class.

Lets have a look of this code!
        abstract class animal
        {
            public abstract void eat ();
            public void sound ()
            {
                Console.WriteLine("dog can sound");
            }
        }

This is the Abstract Base Class, if i do both of its methods abstract then this class would become pure Abstract Base Class.

Now we derive a class of 'dog' from the class animal.

abstract class animal
        {
            public abstract void eat ();
            public void sound ()
            {
                Console.WriteLine("dog can sound");
            }
        }

        class dog : animal
        {
            public override void eat() { Console.WriteLine("dog can eat"); }
        }

Here you can see we have 2 methods in the Abstract Base Class, the method eat() has no implementation that is why it is being declared as 'abstract' while the method sound() has its own body so it is not declared as 'abstract'.

In the derived class we have the same name method but this method has got its body.

We are doing abstraction here so that we can access the method of derived class without any trouble.

Let’s have a look!

class program
    {
        abstract class animal
        {
            public abstract void eat();
            public void sound()
            {
                Console.WriteLine("dog can sound");
            }
        }

        class dog : animal
        {
            public override void eat() { Console.WriteLine("dog can eat"); }
        }

        static void Main(string[] args)
        {
            dog mydog = new dog();
            animal thePet = mydog;
            thePet.eat();
            mydog.sound();
        }
  }

Finally we created an Object 'mydog' of class dog, but we didn't instantiate any object of Abstract Base Class 'animal'.

According to "Ivor Horton"(a programmer of Java) an object can not be instantiated, but we can declare a variable of the Abstract Class type. If this statement is true then it could be possible :

    animal thePet;

This is an object which is declared as thePet and its data type is the abstract base class 'animal'.

We can use this Object to store Objects of the subclass.

In the above code we declare an Object 'thePet', of the type animal(the Abstract Base Class) and simply copied the object of another object(only the reference is copied as they belong to reference type).Now we can use object 'thePet' just as object 'mydog'. 

The output of this code would be as     

        dog can eat
      dog can sound 

Conclusion: 

 
l conclude here by saying that Abstraction is not a difficult job to do, but you need to be confident while performing abstraction. Our every new topic covers the all previous topics. In the abstraction the polymorphism is being covered and performed. Everything is possible in Programming and there are multiple ways to do a single job. Abstraction is one of the smart way to do these kind of tasks.
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About the Author

Zon
Full Name: Faizan Ahmed
Member Level: Starter
Member Status: Member
Member Since: 8/31/2010 3:43:11 PM
Country: Australia
faizan_ahmed

A B.S graduate, seeking a challenging position in a progressive organization With an aim to contribute positively towards the objectives of The organization and to enhance my professional skills"

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