Présentation

Cyril Findeling đź‘‹

DĂ©veloppement mobile

  • technos moderne
  • performances limitĂ©es
  • livraisons itĂ©ratives
  • domaine compĂ©titif
  • conditions de travail

Ce cours

  • Focus sur Kotlin et Android
  • Notions principales pour dĂ©velopper une app dans un vrai projet
  • Un peu de thĂ©orie surtout au dĂ©but, beaucoup de pratique
  • Un projet fil rouge notĂ© Ă  la fin

OOP: Object Oriented Programming

Vocabulary

  • Type, Primitive, Class, Instance, Generics
  • Variable, Function, Property, Method
  • Inherit, Override, Implement, Abstract

Principles

  • Encapsulation
  • Abstraction
  • Inheritance
  • Polymorphism

Encapsulation

Hide the internal state

Encapsulation: Example

class Cat {
    private var lives = 9

    public fun die() {
        if (lives > 0) lives--
        else print("🙀💀")
    }
}

Abstraction

Expose high level handles

Abstraction Example

class CoffeeMachine {
    private var isWaterHot = false
    private fun makeEspresso() { ... }
    private fun makeLatte() { ... }
    //...

    public fun makeCoffee(coffeeType: CoffeeType) {
        when(coffeeType) {
            Espresso -> makeEspresso()
            Latte -> makeLatte()
            //...
        }
    }
}

Inheritance

Extend an other Class

Inheritance Example

class Animal {
    fun eat() {
        print("nom nom")
    }
}

class Cat : Animal {
    var isBored = false
    override fun eat() {
        if (isBored) {
            super.eat()
        }
    }
}

Interface

interface FriendsDataSource {
    val url: String
    fun getFriends() : List<Friend>
}

class TwitterFriendsDataSource : FriendsDataSource {
    override val url = "https://twitter.com/friends"
    override fun getFriends() : List<Friend> {
        // request from Twitter
    }
}

class FacebookFriendsDataSource : FriendsDataSource {
    override val url = "https://facebook.com/friends"
    override fun getFriends() : List<Friend> {
        // request from Facebook
    }
}

Abstract class

abstract class FriendsDataSource {
    abstract val url: String
    fun getFriends() : List<Friend> {
        return emptyList()
    }
}

class TwitterFriendsDataSource : FriendsDataSource {
    override val url = "https://twitter.com/friends"
    override fun getFriends() : List<Friend> {
        // request from Twitter
    }
}

class FacebookFriendsDataSource : FriendsDataSource {
    override val url = "https://facebook.com/friends"
    override fun getFriends() : List<Friend> {
        // request from Facebook
    }
}

Polymorphism

Use the same code for different types

Polymorphism example

fun calculateTotalSurface(figures: List<Figure>) : Int {
    var totalSurface = 0
    figures.forEach { figure ->
        totalSurface += figure.calculateSurface()
    }
    return totalSurface
}

SOLID principles

  • Single-responsibility: A class should have a single responsibility
  • Open–closed: open for extension, closed for modification
  • Liskov substitution: No changes when replacing objects by their subtypes
  • Interface segregation: Prefer several specific interfaces to a general one
  • Dependency inversion: Depend upon abstractions, not concretions

Other Principles

  • DRY: Don't Repeat Yourself
  • YAGNI: You Are Not Gonna Need It
  • KISS: Keep it simple, stupid
  • SSOT: Single source of truth

Going Further

  • Design Patterns (Singleton, Factory, ...)
  • Dependency Injection
  • Is Inheritance bad ?
  • Often prefer composition: "has-a" VS "is-a"
  • Entity Component System
  • OOP is not a silver bullet

Other Paradigms

  • Procedural Programming
  • Functional Programming
  • Data Oriented Design
  • Reactive Programming