As time passes, the way we develop software changes. It comes with new programming languages, frameworks, libraries, and now paradigms. Object-oriented programming came to change how we build our apps, providing a more maintainable, reusable, and scalable way to build. But in order to do that, you must know all the basics. That's why I am going to teach the four principles of OOP.

Abstraction

Abstraction essentially hides complex implementations and only shows the necessary features of an object.

Within this principle, there are two key topics we must know about:

• Abstract Class: Can't be instantiated and can have abstract methods that must be overridden in the implementing class.
  

  public abstract class AnimeCharacter {
  
      public abstract string SpecialAttack();
  
      public virtual string Goal() {
          return "Save the planet";
      }
  }
  
  public class Goku : AnimeCharacter {
  
      public override string SpecialAttack() {
          return "Kamehameha!!";
      }
  }
  
  public class Gojo : AnimeCharacter {
  
      public override string SpecialAttack() {
          return "Domain expansion";
      }
  
      public override string Goal() {
          return "Defeat Sukuna";
      }
  }
  

  So, what's this virtual keyword 🤔? It allows setting default implementations for methods that can be overridden.

• Interfaces: A contract that the implementing class must define.
  

  public interface IMovable {
  
     string Move();
  }
  
  public class Goku : IMovable {
  
      public string Move() {
          return "Fly";
      }
  }
  
  public class Luffy : IMovable {
  
      public string Move() {
          return "Run";
      }
  }
  

Encapsulation

Encapsulation is a shield that prevents a piece of code from being accessed outside its scope.

With access modifiers, you can restrict access to your code:

• Public: The code has no restrictions.
• Private: The code can only be accessed within the class itself.
• Protected: Only the superclass and subclass can access the code.
• Internal: The code has restrictions within the same assembly/project.

    public class AnimeCharacter {

        // Private field
        private string secretTechnique;

        // Public property
        public string Name { get; set; }

        // Protected property
        protected string Rank { get; set; }

        // Public method to set the private field
        public void SetSecretTechnique(string technique) {
            secretTechnique = technique;
        }

        // Public method to get the private field
        public string GetSecretTechnique() {
            return secretTechnique;
        }
    }

    public class Ninja : AnimeCharacter {

        // Public method to access the protected property
        public void SetRank(string rank) {
            Rank = rank;
        }

        // Public method to get the protected property
        public string GetRank() {
            return Rank;
        }
    }

    var naruto = new Ninja();
    naruto.Name = "Naruto Uzumaki";
    naruto.SetSecretTechnique("Shadow Clone Jutsu");
    naruto.SetRank("Genin");

    naruto.Name; // Outputs "Naruto Uzumaki"
    naruto.GetSecretTechnique() // Outputs "Shadow Clone Jutsu"
    naruto.GetRank(); // Outputs "Genin"

Inheritance

Inheritance allows methods and properties to be inherited from another class.

• Superclass or Parent Class
  

  public class Minato {
  
     public string HairColor = "yellow";
  
     public string Attack() {
         return "Rasengan!!";
     }
  }
  

• Subclass or Child Class
  

  public class Naruto : Minato {
     public string FavoriteFood = "ramen";
  
     public string Attack() {
         return "Rasengan!!";
     }
  }
  
  var naruto = new Naruto();
  naruto.HairColor; // Outputs "yellow"
  

Polymorphism

Polymorphism allows classes to have different implementations of methods that are called by the same name.

It comes in two forms:

• Compile-time (method overload)
  

  public class Zoro {
  
      // Method overload for attack
      public string Attack(int swords) {
          return $"Attacks with {swords} swords.";
      }
  
      // Method overload for a named attack
      public string Attack(string technique) {
          return $"Uses the technique {technique}.";
      }
  }
  
  var zoro = new Zoro();
  zoro.Attack(3);                // Outputs "Attacks with 3 swords."
  zoro.Attack("Santoryu Ogi");   // Outputs "Uses the technique Santoryu Ogi."
  

• Run-time (method override)
  

  public class AnimeCharacter {
  
      public virtual string SpecialMove() {
          return "Basic Attack";
      }
  }
  
  public class Ichigo : AnimeCharacter {
  
      public override string SpecialMove() {
          return "Getsuga Tensho";
      }
  }
  
  public class Sasuke : AnimeCharacter {
  
      public override string SpecialMove() {
          return "Chidori";
      }
  }
  
  AnimeCharacter ichigo = new Ichigo();
  AnimeCharacter sasuke = new Sasuke();
  ichigo.SpecialMove();  // Outputs "Getsuga Tensho"
  sasuke.SpecialMove();  // Outputs "Chidori"
  

Conclusion

Now you know the four principles of Object-Oriented Programming: Encapsulation, which allows you to restrict access by scope; Abstraction, which shows valuable features while hiding complex implementations; Inheritance, which enables you to reuse fields and methods; and Polymorphism, which allows you to change behavior at compile time and run time. Happy coding!