"Subclassing Structs" - dotSwift 2017

Presentation from dotSwift 2017 conference, in Paris, Jan 2017.
Vidéo: https://www.dotconferences.com/2017/01/dimitri-dupuis-latour-subclassing-structs

In this lightning talk (4"), I describe a pattern I use in my ‘struct’ objects to have some form of ‘class’ hierarchy, without using ‘classes’. How do you subclass a struct ? Answer: Enums, Associated values and Composition…

Transcript

1. SUBCLASSING STRUCTS Dimitri Dupuis-Latour
 Freelance iOS Dev, Former Apple Engineer
 @dupuislatour dupuislatour@me.com
2. STRUCTS ARE AWESOME
3. Design with struct as the default, fallback to class as last resort
4. 1. VALUE SEMANTICS
5. 2. SPEED !
6. 40X FASTER SWIFT 1.0 struct vs class
7. 37 000 000X FASTER SWIFT 2.0 - WHOLE MODULE OPTIMIZATION struct vs class github.com/knguyen2708/StructVsClassPerformance
8. 3. AUTOMATIC INITIALIZER
9. struct Post { let date: Date let author: String let text: String }
10. 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 !")
11. 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 } ✗
12. PROBLEM:
 HOW DO YOU SUBCLASS ?
13. struct Post { let date: Date let author: String let likes: Int = 0 let comments: [String] = [] let text: String }
14. 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? }
15. 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? } ✗
16. 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
17. 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
18. 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
19. SOLUTIONS
20. SUBCLASSING ? class Post {} class TextPost : Post {} class ImagePost : Post {} class VideoPost : Post {}
21. PROTOCOLS ? protocol Textable {} protocol Imagable {} protocol Videoable {}
22. ENUMS ! enum PostType { case text case image case video }
23. ENUMS ! enum PostType { case text(text:String) case image(image:UIImage, legend:String) case video(url: URL, duration: TimeInterval) }
24. 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? }
25. struct Post { let date: Date let author: String let likes: Int = 0 let comments: [String] = [] let type: PostType }
26. 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))
27. THANKS ! Dimitri Dupuis-Latour
 Freelance iOS Dev, Former Apple Engineer
 @dupuislatour dupuislatour@me.com