C23-Abstraction.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CSharp_CheatSheet
{
    internal class C23_Abstraction
    {
        // Abstract Classes and Methods

        // Data abstraction is the process of hiding certain details and showing only essential information to the user.
        // Abstraction can be achieved with either abstract classes or interfaces.

        // The abstract keyword is used for classes and methods:
        //      - Abstract class: is a restricted class that cannot be used to create objects(to access it, it must be inherited from another class).
        //      - Abstract method: can only be used in an abstract class, and it does not have a body.The body is provided by the derived class (inherited from).

        // An abstract class can have both abstract and regular methods:
        abstract class AnimalExample
        {
            public abstract void animalSound();
            public void sleep()
            {
                Console.WriteLine("Zzz");
            }
        }

        // From the example above, it is not possible to create an object of the Animal class:

        AnimalExample myObj = new AnimalExample(); // Will generate an error (Cannot create an instance of the abstract class or interface 'Animal')

        // To access the abstract class, it must be inherited from another class.
        // Let's convert the Animal class we used in the Polymorphism chapter to an abstract class.
        // Remember from Inheritance that we use the : symbol to inherit from a class, and that we use the override keyword to override the base class method.

        // Abstract class
        abstract class Animal
        {
            // Abstract method (does not have a body)
            public abstract void animalSound();
            // Regular method
            public void sleep()
            {
                Console.WriteLine("Zzz");
            }
        }

        // Derived class (inherit from Animal)
        class Pig : Animal
        {
            public override void animalSound()
            {
                // The body of animalSound() is provided here
                Console.WriteLine("The pig says: wee wee");
            }
        }

        class Program
        {
            static void Main(string[] args)
            {
                Pig myPig = new Pig(); // Create a Pig object
                myPig.animalSound();  // Call the abstract method
                myPig.sleep();  // Call the regular method
            }
        }

        // Why And When To Use Abstract Classes and Methods?
        // To achieve security - hide certain details and only show the important details of an object.
        // Note: Abstraction can also be achieved with Interfaces
    }
}