OOP Principles

Abstraction

Can be achieved by:

• Exposing a limited set of public methods

• Exposing an interface

• In statically typed languages abstract base classes(ABC) or Interfaces are used to define abstractions. Same can be achieved in dynamically typed languages such as python/js using duck typing

  class Duck:
      def quacks(self):
          print("Imma duck")
  
  class Frog:
      def quacks(self):
          print("Imma frog")
  
  def quack(qackable):
      # Anything that can quack will quack
      # We're good as long as the signature matches
      qackable.quacks();
  
  quack(Duck())
  quack(Frog())

Encapsulation

Amplify the essential while suppressing the details.

• public access modifiers are self documenting API's of a class. A well chosen limited set of public methods amplifies the essentials to the users.
• private access modifiers restrict the scope of altering the internal state in an unintended way.

Polymorphism

• Ad-hoc : Method overload

    void print(Person person) {
        System.out.printf("Name %s Age %d", person.name, person.age);
    }

    void print(Company company) {
        System.out.printf("Name %s Age %d", company.name);
    }

• sub-typing: Inheritance, method override. Reduced multiple if statements to 1(construction)