Polymorphism

  • Principle of OOP
  • What is Polymorphism?
  • Code improvement using polymorphism
  • Polymorphism in SOLID principle
  • Polymorphism in Design Pattern

Principles of OOP

Encapsulation

Abstraction

Inheritance

Polymorphism

Recap

What is Inheritance?

child class can reuse attribute and method in parent class

Without Inheritance

Inheritance

What is Polymorphism?

  • the ability to take different forms
  • use same method but do differently

many

forms

Animal = [

]

,

,

function makeSound(animal: String){

    if(animal === "dog"){
        console.log("bark bark bark")
    }else if(animal === "cat"){
        console.log("meow meow")
    }else if(animal === "cow"){
        console.log("moo")
    }
}
function makeSound(animal: String){

  switch(animal) { 
      case "dog": 
          console.log("bark bark bark"); 
          break; 
      case "cat": 
          console.log("meow meow"); 
          break; 
      case "cow": 
          console.log("moo"); 
          break;
      default:
          break;
  } 
}

BEFORE

function makeSound(animal: Animal){
    animal.makeSound();
}

AFTER

class Animal {
  
  private name: String;
  
  constructor(name){
    this.name = name;
  }
  
  makeSound() {
    console.log("blablabla")
  }
}
class Dog extends Animal {
  makeSound() {
    console.log("bark bark bark")
  }
}
class Cat extends Animal {
  makeSound() {
    console.log("meow meow")
  }
}
class Cow extends Animal {
  makeSound() {
    console.log("moo")
  }
}
const animals = [new Dog("a"), new Cat("b"), new Cow("c")];
animals.map(animal => animal.makeSound());

// bark bark bark
// meow meow
// moo

Polymorphism

https://slides.com/max_57070/programmers-quadrant#/3/2

interface Occupation {
    doJob(): void;
}
  
class Cow {
    private name: string

    constructor(name: string){
        this.name = name;
    }

    public makeSound(): void {
        console.log("moo")
    }

}
  
class SportCow extends Cow implements Occupation {
    public doJob(): void {
        console.log("provide bull riding")
    }
}

class MilkCow extends Cow implements Occupation {
    public doJob(): void {
        console.log("provide milk")
    }
}

class MeatCow extends Cow implements Occupation {
    public doJob(): void {
        console.log("provide meat")
    }
}
  
const cowOccupations = [new SportCow("a"), new MilkCow("b"), new MeatCow("c")];
cowOccupations.map(occupation => occupation.doJob());

IMPROVE CURRENT CODE USING

POLYMORPHISM

Which SOLID principle used polymorphism?

S - Single Responsible Principle

O - Open Closed Principle

L - Liskov Substitution Principle

I - Interface Segregation Principle

D - Dependency Inversion Principle

Example of design pattern used polymorphism

Strategy Pattern

Factory Pattern

polymorphism

By shirlin1028

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