Kotlin For Swift Developers - Swift Paris, October 2018

Kotlin is a new language born on the JVM that's gained a ton of popularity with Android developers. Learn about its similarities and differences with Swift, and some new, crazy things you can do with Kotlin/Native (and some totally sane things you can't do).

Sandbox app mentioned in the talk: https://github.com/designatednerd/KotlinNativeTest

Transcript

1. KOTLIN FOR SWIFT DEVELOPERS SWIFT PARIS | PARIS, FRANCE | OCTOBER 2018 @DESIGNATEDNERD | BAKKENBAECK.COM | JUSTHUM.COM
2. KOTLIN POUR SWIFT DEVELOPPEURS SWIFT PARIS ! PARIS, FRANCE OCTOBRE 2018 @DESIGNATEDNERD ! BAKKENBAECK.COM JUSTHUM.COM
3. !"
11. ✨ " ☕
13. WHAT IS KOTLIN ?
18. WHY SHOULD I CARE?
21. A CONSTANT STRING
22. SWIFT let greeting = "Hello World"
23. SWIFT let greeting = "Hello World" KOTLIN val greeting = "Hello World"
24. AN OPTIONAL INTEGER VARIABLE
25. SWIFT var something: Int?
26. SWIFT var something: Int? KOTLIN var something: Int?
27. ☠ NullPointerException
28. !"
29. GENERICS AND FUNCTIONS AS PARAMETERS
30. SWIFT func useFunction<T, U>(on item: T, function: (T) -> U) -> U { return function(item) } func insertExclamationPoint(in string: String) -> String { return string .components(separatedBy: " ") .joined(separator: "! ") } let result = useFunction(on: "try Swift", function: insertExclamationPoint(in:)) // result: "try! Swift"
31. KOTLIN fun <T, U>T.useFunction(action: (T) -> U): U { return action(this) } fun insertExclamationPoint(in: String) : String { return in.split(" ").joinToString("! ") } val result = "try Kotlin".useFunction { insertExclamationPoint(it) } // result: "try! Kotlin"
32. map filter reduce
33. map filter reduce*
34. SWIFT let numbers = [ 1, 2, 3 ] let reduced = numbers.reduce(0, +) // reduced: 6
35. SWIFT let numbers = [ 1, 2, 3 ] let reduced = numbers.reduce(0, +) // // reduced: 6
36. SWIFT let numbers = [ 1, 2, 3 ] let reduced = numbers.reduce(0) { $0 + $1 } // reduced: 6
37. SWIFT let numbers = [ 1, 2, 3 ] let reduced = numbers.reduce(20) { $0 + $1 } // reduced: 26
38. SWIFT let numbers = [ 1, 2, 3 ] let reduced = numbers.reduce(20) { $0 + $1 } // reduced: 26 KOTLIN val numbers = arrayOf(1, 2, 3) val reduced = numbers.reduce { total, current -> total + current } // reduced: 6
39. SWIFT let numbers = [ 1, 2, 3 ] let reduced = numbers.reduce(20) { $0 + $1 } // reduced: 26 ⬆ KOTLIN val numbers = arrayOf(1, 2, 3) val reduced = numbers.reduce { total, current -> total + current } // reduced: 6
40. SWIFT let numbers = [ 1, 2, 3 ] let reduced = numbers.reduce(20) { $0 + $1 } // reduced: 26 KOTLIN val numbers = arrayOf(1, 2, 3) val folded = numbers.fold(20) ⬅ { total, current -> total + current } // folded: 26
41. SWIFT let doubled = [ 1, 2, 3 ].map { $0 * 2 }
42. SWIFT let doubled = [ 1, 2, 3 ].map { $0 * 2 } KOTLIN arrayOf(1, 2, 3).map { it * 2 }
45. SWIFT let doubled = [ 1, 2, 3 ].map { $0 * 2 } KOTLIN arrayOf(1, 2, 3).map { it * 2 }
46. SWIFT let numbers = [ 1, 2, 3 ] let reduced = numbers.reduce(20) { $0 + $1 } // reduced: 26
47. $0 $1 $2...$∞
48. SWIFT let numbers = [ 1, 2, 3 ] let reduced = numbers.reduce(20) { $0 + $1 } // reduced: 26 KOTLIN val numbers = arrayOf(1, 2, 3) val folded = numbers.fold(20) { total, current -> total + current } // folded: 26 ⬆
50. !"#
52. guard
53. NOW (KOTLIN) optionalThing?.let { it.doSomething() }
54. NOW (KOTLIN) optionalThing?.let { it.doSomething() } else { doSomethingElse() }
55. NOW (KOTLIN) optionalThing?.let { it.doSomething() } else { // ! Not possible doSomethingElse() }
56. NOW (KOTLIN) if (optionalThing != nil) { optionalThing.doSomething() } else { doSomethingElse() }
57. NOW (KOTLIN) if (optionalThing != nil) { optionalThing.doSomething() //<- magic unwrap!! } else { doSomethingElse() }
58. PROPOSED (KOTLIN) guard val thing = optionalThing else { return } thing.doSomething()
59. apply
60. NOW (SWIFT) UserDefaults.standard.set(true, forKey: "DefaultOne") UserDefaults.standard.set(false, forKey: "DefaultTwo)
61. NOW (BETTER SWIFT) let defaults = UserDefaults.standard defaults.set(true, forKey: "DefaultOne") defaults.set(false, forKey: "DefaultTwo)
62. PROPOSED (SWIFT) UserDefaults.standard.apply { "DefaultOne" = true, "DefaultTwo" = false, }
63. PROTOCOLS WITH DEFAULT IMPLEMENTATIONS
65. PROPOSED (KOTLIN) interface SomeInterface { fun doAThing() }
66. PROPOSED (KOTLIN) interface SomeInterface { fun doAThing() } @DefaultImpl SomeInterface { fun doAThing() { println("Hi, I'm the default implementation!") } }
67. @JVMDefault + DefaultImpl (SORT OF)
68. SEALED CLASSES
69. KOTLIN sealed class ViewState { class Empty(val placeholder: View): ViewState() class HasContent(val items: List<Item>): ViewState() }
70. KOTLIN sealed class ViewState { class Empty(val placeholder: View): ViewState() class HasContent(val items: List<Item>): ViewState() } when (state) { is ViewState.Empty --> display(it.placeholder) is ViewState.HasContent --> adapter.reloadWith(it.items) }
71. SWIFT enum TableViewState { case empty(placeholderView: UIView) case loaded(items: [Item]) } switch state { case .empty(let placeholder): display(placeholder) case .hasContent(let items): dataSource.reloadWith(items) }
72. KOTLIN sealed class ViewState { class Empty(val placeholder: View): ViewState() class HasContent(val items: List<Item>): ViewState() }
73. KOTLIN sealed class ViewState { class Empty(val placeholder: View): ViewState() class HasContent(val items: List<Item>): ViewState() { val adapter = RecyclerViewAdapter(items) fun selectedItem(item: Item) { // Do something ith the selected item } } }
74. ☕
77. KOTLIN / NATIVE
79. PLUS ÇA CHANGE
80. LLVM
81. LLVM
82. LLVM
83. SUPPORTED PLATFORMS ▸ x86_64 (macOS, iOS Sim, Linux, Windows) ▸ arm64 (iOS, Android) ▸ arm32 (iOS, Android, Linux) ▸ arm32 hardfp (Raspberry Pi) ▸ MIPS (Linux) ▸ wasm32 (Web Assembly)
88. expect fun
92. KOTLIN IOS LIBRARY ! WRAPPERS
96. KOTLIN IOS LIBRARY ! WRAPPERS* *(WHICH USUALLY WORK)
97. KOTLIN / NATIVE val decoded = NSString.create( data = data, encoding = NSUTF8StringEncoding )
98. KOTLIN / NATIVE val decoded = NSString.create( data = data, encoding = NSUTF8StringEncoding ) // `decoded` type: NSString
105. BUSINESS LOGIC
108. KOTLIN / NATIVE GOTCHAS
109. !
110. + =
111. MEMORY MANAGEMENT AND CONCURRENCY !!!!!!!
112. COROUTINES
113. COROUTINES* * ONLY WORK ON THE MAIN THREAD IN KOTLIN / NATIVE
114. (˽s̕s҂˽Ɨ ˍʓˍ
115. Worker
116. ! MONOREPO
117. https://github.com/designatednerd/ KotlinNativeTest
118. OBJ-C INTEROP HILARITY
119. SWIFT: ENUMS enum Things { case monday case tuesday case wednesday case thursday case friday case saturday case sunday }
120. KOTLIN: ENUM CLASSES enum class DayOfWeek { Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday; }
122. A KOTLIN ENUM CLASS IN A KOTLIN / NATIVE FRAMEWORK
123. A KOTLIN ENUM CLASS IN A KOTLIN / NATIVE FRAMEWORK
124. A KOTLIN ENUM CLASS IN A KOTLIN / NATIVE FRAMEWORK
125. SWIFT SWITCHING ON A KOTLIN ENUM switch day { case .monday: print("You can fall apart") case .tuesday, .wednesday: print("Break my heart") case .thursday: print("Doesn't even start") case .friday: print("I'm in love") case .saturday: print("Wait") case .sunday: print("Always comes too late") } // ! Seems legit...
126. SWIFT SWITCHING ON A KOTLIN ENUM switch day { case .monday: print("You can fall apart") case .tuesday, .wednesday: print("Break my heart") case .thursday: print("Doesn't even start") case .friday: print("I'm in love") case .saturday: print("Wait") case .sunday: print("Always comes too late") } // ! ERROR: ! Switch must be exhaustive
127. SWIFT SWITCHING ON A KOTLIN ENUM switch day { case .monday: print("You can fall apart") case .tuesday, .wednesday: print("Break my heart") case .thursday: print("Doesn't even start") case .friday: print("I'm in love") case .saturday: print("Wait") case .sunday: print("Always comes too late") default: fatalError("Not a day") // ! }
128. DOCUMENTATION
129. DOCUMENTATION? ¯\_(ϑ)_/¯
131. PRODUCTION?!
132. KOTLIN: ☕ OR " =
133. try? kotlin
134. https://try.kotlinlang.org
137. EDU TOOLS PLUGIN FOR INTELLIJ OR ANDROID STUDIO
140. OBLIGATORY SUMMARY SLIDE
141. OBLIGATORY SUMMARY SLIDE ▸ Literally put the fun in functional programming
142. OBLIGATORY SUMMARY SLIDE ▸ Literally put the fun in functional programming ▸ Make Friends With Android
143. OBLIGATORY SUMMARY SLIDE ▸ Literally put the fun in functional programming ▸ Make Friends With Android ▸ Kotlin Native Could Be A Whole New World
144. OBLIGATORY SUMMARY SLIDE ▸ Literally put the fun in functional programming ▸ Make Friends With Android ▸ Kotlin Native Could Be A Whole New World ▸ try! Kotlin
145. ONE MORE THING
146. ONE MORE THING: (A SHAMELESS PLUG!)
148. ! MERÇI!
149. LINKS! ▸ Kotlin Home & Documentation: https://kotlinlang.org ▸ Kotlin Native MultiplatformApp tutorial https://kotlinlang.org/docs/tutorials/ native/mpp-ios-android.html ▸ KotlinConf iOS App in Kotlin/Native: https://github.com/JetBrains/kotlinconf- app/tree/master/konfios
150. MORE LINKS! ▸ The Edu Tools Plugin for IntelliJ or Android Studio https://kotlinlang.org/docs/tutorials/ edu-tools-learner.html ▸ Representing State (KotlinConf talk on Sealed Classes) https://www.youtube.com/watch?v=- lVVfxsRjcY ▸ Sealed Classes Opened My Mind (KotlinConf Talk) https://www.youtube.com/watch? v=uGMm3StjqLI
151. SHAMELESS SELF-PROMOTION! ▸ My talk on Protocol-Oriented Programming from Dot Swift https://www.dotconferences.com/2018/01/ ellen-shapiro-protocols-all-the-way-down ▸ Kotlin Apprentice https://store.raywenderlich.com/products/ kotlin-apprentice ▸ Android Apprentice https://store.raywenderlich.com/products/ android-apprentice
152. ILLUSTRATION CREDITS ▸ Monica Komperda, Native Code Forever (Hire her! She's awesome!) http://mokomperda.com/design