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
   

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2. KOTLIN
   POUR SWIFT DEVELOPPEURS
   SWIFT PARIS
   !
   PARIS, FRANCE OCTOBRE 2018
   @DESIGNATEDNERD
   !
   BAKKENBAECK.COM JUSTHUM.COM
   

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3. !"
   

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11. ✨ " ☕
    

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13. WHAT IS KOTLIN ?
    

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18. WHY SHOULD I CARE?
    

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21. A CONSTANT STRING
    

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22. SWIFT
    let greeting = "Hello World"
    

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23. SWIFT
    let greeting = "Hello World"
    KOTLIN
    val greeting = "Hello World"
    

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24. AN OPTIONAL INTEGER VARIABLE
    

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25. SWIFT
    var something: Int?
    

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26. SWIFT
    var something: Int?
    KOTLIN
    var something: Int?
    

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27. ☠
    NullPointerException
    

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28. !"
    

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29. GENERICS
    AND
    FUNCTIONS AS PARAMETERS
    

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30. SWIFT
    func useFunction(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"
    

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31. KOTLIN
    fun 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"
    

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32. map
    filter
    reduce
    

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33. map
    filter
    reduce*
    

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34. SWIFT
    let numbers = [ 1, 2, 3 ]
    let reduced = numbers.reduce(0, +)
    // reduced: 6
    

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35. SWIFT
    let numbers = [ 1, 2, 3 ]
    let reduced = numbers.reduce(0, +) //
    // reduced: 6
    

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36. SWIFT
    let numbers = [ 1, 2, 3 ]
    let reduced = numbers.reduce(0) { $0 + $1 }
    // reduced: 6
    

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37. SWIFT
    let numbers = [ 1, 2, 3 ]
    let reduced = numbers.reduce(20) { $0 + $1 }
    // reduced: 26
    

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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
    

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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
    

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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
    

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41. SWIFT
    let doubled = [ 1, 2, 3 ].map { $0 * 2 }
    

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42. SWIFT
    let doubled = [ 1, 2, 3 ].map { $0 * 2 }
    KOTLIN
    arrayOf(1, 2, 3).map { it * 2 }
    

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45. SWIFT
    let doubled = [ 1, 2, 3 ].map { $0 * 2 }
    KOTLIN
    arrayOf(1, 2, 3).map { it * 2 }
    

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46. SWIFT
    let numbers = [ 1, 2, 3 ]
    let reduced = numbers.reduce(20) { $0 + $1 }
    // reduced: 26
    

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47. $0 $1 $2...$∞
    

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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
    ⬆
    

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50. !"#
    

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52. guard
    

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53. NOW (KOTLIN)
    optionalThing?.let {
    it.doSomething()
    }
    

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54. NOW (KOTLIN)
    optionalThing?.let {
    it.doSomething()
    } else {
    doSomethingElse()
    }
    

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55. NOW (KOTLIN)
    optionalThing?.let {
    it.doSomething()
    } else { //
    !
    Not possible
    doSomethingElse()
    }
    

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56. NOW (KOTLIN)
    if (optionalThing != nil) {
    optionalThing.doSomething()
    } else {
    doSomethingElse()
    }
    

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57. NOW (KOTLIN)
    if (optionalThing != nil) {
    optionalThing.doSomething() //<- magic unwrap!!
    } else {
    doSomethingElse()
    }
    

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58. PROPOSED (KOTLIN)
    guard val thing = optionalThing else {
    return
    }
    thing.doSomething()
    

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59. apply
    

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60. NOW (SWIFT)
    UserDefaults.standard.set(true, forKey: "DefaultOne")
    UserDefaults.standard.set(false, forKey: "DefaultTwo)
    

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61. NOW (BETTER SWIFT)
    let defaults = UserDefaults.standard
    defaults.set(true, forKey: "DefaultOne")
    defaults.set(false, forKey: "DefaultTwo)
    

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62. PROPOSED (SWIFT)
    UserDefaults.standard.apply {
    "DefaultOne" = true,
    "DefaultTwo" = false,
    }
    

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63. PROTOCOLS WITH
    DEFAULT IMPLEMENTATIONS
    

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65. PROPOSED (KOTLIN)
    interface SomeInterface {
    fun doAThing()
    }
    

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66. PROPOSED (KOTLIN)
    interface SomeInterface {
    fun doAThing()
    }
    @DefaultImpl
    SomeInterface {
    fun doAThing() {
    println("Hi, I'm the default implementation!")
    }
    }
    

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67. @JVMDefault + DefaultImpl
    (SORT OF)
    

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68. SEALED CLASSES
    

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69. KOTLIN
    sealed class ViewState {
    class Empty(val placeholder: View): ViewState()
    class HasContent(val items: List): ViewState()
    }
    

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70. KOTLIN
    sealed class ViewState {
    class Empty(val placeholder: View): ViewState()
    class HasContent(val items: List): ViewState()
    }
    when (state) {
    is ViewState.Empty --> display(it.placeholder)
    is ViewState.HasContent --> adapter.reloadWith(it.items)
    }
    

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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)
    }
    

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72. KOTLIN
    sealed class ViewState {
    class Empty(val placeholder: View): ViewState()
    class HasContent(val items: List): ViewState()
    }
    

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73. KOTLIN
    sealed class ViewState {
    class Empty(val placeholder: View): ViewState()
    class HasContent(val items: List): ViewState() {
    val adapter = RecyclerViewAdapter(items)
    fun selectedItem(item: Item) {
    // Do something ith the selected item
    }
    }
    }
    

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74. ☕
    

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77. KOTLIN / NATIVE
    

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79. PLUS ÇA CHANGE
    

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80. LLVM
    

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81. LLVM
    

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82. LLVM
    

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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)
    

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88. expect fun
    

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92. KOTLIN IOS LIBRARY
    !
    WRAPPERS
    

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96. KOTLIN IOS LIBRARY
    !
    WRAPPERS*
    *(WHICH USUALLY WORK)
    

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97. KOTLIN / NATIVE
    val decoded = NSString.create(
    data = data,
    encoding = NSUTF8StringEncoding
    )
    

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98. KOTLIN / NATIVE
    val decoded = NSString.create(
    data = data,
    encoding = NSUTF8StringEncoding
    )
    // `decoded` type: NSString
    

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105. BUSINESS LOGIC
     

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108. KOTLIN / NATIVE GOTCHAS
     

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109. !
     

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110. + =
     

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111. MEMORY MANAGEMENT
     AND CONCURRENCY
     !!!!!!!
     

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112. COROUTINES
     

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113. COROUTINES*
     * ONLY WORK ON THE MAIN THREAD IN KOTLIN / NATIVE
     

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114. (˽s̕s҂˽Ɨ ˍʓˍ
     

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115. Worker
     

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116. !
     MONOREPO
     

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117. https://github.com/designatednerd/
     KotlinNativeTest
     

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118. OBJ-C INTEROP HILARITY
     

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119. SWIFT: ENUMS
     enum Things {
     case monday
     case tuesday
     case wednesday
     case thursday
     case friday
     case saturday
     case sunday
     }
     

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120. KOTLIN: ENUM CLASSES
     enum class DayOfWeek {
     Monday,
     Tuesday,
     Wednesday,
     Thursday,
     Friday,
     Saturday,
     Sunday;
     }
     

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122. A KOTLIN ENUM CLASS IN A KOTLIN / NATIVE FRAMEWORK
     

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123. A KOTLIN ENUM CLASS IN A KOTLIN / NATIVE FRAMEWORK
     

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124. A KOTLIN ENUM CLASS IN A KOTLIN / NATIVE FRAMEWORK
     

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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...
     

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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
     

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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") //
     !
     }
     

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128. DOCUMENTATION
     

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129. DOCUMENTATION?
     ¯\_(ϑ)_/¯
     

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131. PRODUCTION?!
     

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132. KOTLIN:
     ☕
     OR
     "
     =
     

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133. try? kotlin
     

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134. https://try.kotlinlang.org
     

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137. EDU TOOLS
     PLUGIN FOR INTELLIJ OR ANDROID STUDIO
     

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140. OBLIGATORY SUMMARY SLIDE
     

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141. OBLIGATORY SUMMARY SLIDE
     ▸ Literally put the fun in functional programming
     

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142. OBLIGATORY SUMMARY SLIDE
     ▸ Literally put the fun in functional programming
     ▸ Make Friends With Android
     

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143. OBLIGATORY SUMMARY SLIDE
     ▸ Literally put the fun in functional programming
     ▸ Make Friends With Android
     ▸ Kotlin Native Could Be A Whole New World
     

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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
     

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145. ONE MORE THING
     

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146. ONE MORE THING:
     (A SHAMELESS PLUG!)
     

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148. !
     MERÇI!
     

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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
     

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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
     

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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
     

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152. ILLUSTRATION CREDITS
     ▸ Monica Komperda, Native Code Forever
     (Hire her! She's awesome!)
     http://mokomperda.com/design
     

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