SUBCLASSING STRUCTS Dimitri Dupuis-Latour
 Freelance iOS Dev, Former Apple Engineer
 @dupuislatour dupuislatour@me.com

STRUCTS ARE AWESOME

Design with struct as the default, fallback to class as last resort

1. VALUE SEMANTICS

2. SPEED !

40X FASTER SWIFT 1.0 struct vs class

37 000 000X FASTER SWIFT 2.0 - WHOLE MODULE OPTIMIZATION struct vs class github.com/knguyen2708/StructVsClassPerformance

3. AUTOMATIC INITIALIZER

struct Post { let date: Date let author: String let text: String }

struct Post { let date: Date let author: String let text: String } let myPost = Post(date: Date(), author: "Dimitri", text: "I'm on stage at dotSwift 2017 !")

struct Post { let date: Date let author: String let text: String } let myPost = Post(date: Date(), author: "Dimitri", text: "I'm on stage at dotSwift 2017 !") init(date: Date, author: String, text: String) { self.date = date self.author = author self.text = text } ✗

PROBLEM:
 HOW DO YOU SUBCLASS ?

struct Post { let date: Date let author: String let likes: Int = 0 let comments: [String] = [] let text: String }

struct Post { let date: Date let author: String let likes: Int = 0 let comments: [String] = [] let text: String? let image: UIImage? let imageLegend: String? let videoURL: URL? let videoDuration: TimeInterval? }

struct Post { let date: Date let author: String let likes: Int = 0 let comments: [String] = [] let text: String? let image: UIImage? let imageLegend: String? let videoURL: URL? let videoDuration: TimeInterval? } ✗

struct Post { let date: Date let author: String let likes: Int = 0 let comments: [String] = [] let text: String? let image: UIImage? let imageLegend: String? let videoURL: URL? let videoDuration: TimeInterval? } ✗ 1. Memory

struct Post { let date: Date let author: String let likes: Int = 0 let comments: [String] = [] let text: String? let image: UIImage? let imageLegend: String? let videoURL: URL? let videoDuration: TimeInterval? } ✗ 1. Memory 2. Semantic

struct Post { let date: Date let author: String let likes: Int = 0 let comments: [String] = [] let text: String? let image: UIImage? let imageLegend: String? let videoURL: URL? let videoDuration: TimeInterval? } ✗ 1. Memory 2. Semantic 3. Optional

SOLUTIONS

SUBCLASSING ? class Post {} class TextPost : Post {} class ImagePost : Post {} class VideoPost : Post {}

PROTOCOLS ? protocol Textable {} protocol Imagable {} protocol Videoable {}

ENUMS ! enum PostType { case text case image case video }

ENUMS ! enum PostType { case text(text:String) case image(image:UIImage, legend:String) case video(url: URL, duration: TimeInterval) }

struct Post { let date: Date let author: String let likes: Int = 0 let comments: [String] = [] let text: String? let image: UIImage? let imageLegend: String? let videoURL: URL? let videoDuration: TimeInterval? }

struct Post { let date: Date let author: String let likes: Int = 0 let comments: [String] = [] let type: PostType }

let textPost = Post(date: Date(), author: "Dimitri", type: .text(text: "I'm on stage!")) let imagePost = Post(date: Date(), author: "Dimitri", type: .image(image: UIImage(), legend: "Vacation picture")) let videoPost = Post(date: Date(), author: "Dimitri", type: .video(url: URL(string: "youtu.be/abc")!, duration: 60))

THANKS ! Dimitri Dupuis-Latour
 Freelance iOS Dev, Former Apple Engineer
 @dupuislatour dupuislatour@me.com