Kotlin/Native - DevFest Strasbourg 2019

Kotlin/Native... what's that?
How does it work?
It permits to use Kotlin code in iOS app written in Swift, but how?
Can we use it in production?

Let met explain this project made by JetBrains which has the aim to run Kotlin binaries on many platforms. I will also make a return of experience with the integration of Kotlin code as Xcode framework for an iOS app, with its benefits and limits.

This talk has been made for DevFest Strasbourg 2019.
Slidedeck under CC-BY-SA.

You enjoyed reading these slides? Buy me a beer, thanks<3
(https://pylapersonne.info/buymeacoffee)

Transcript

1. Release 5 – 24/10/2019 ✿✿✿✿ ʕ •ᴥ•ʔ/ ︻デ═⼀一 This document is available under terms of Creative Commons with CC-BY-SA 3.0
   

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2. Pierre-Yves Lapersonne
   Android & iOS apps developer
   pylapersonne.info @pylapp
   

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3. KOTLIN
   NATIVE
   

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4. ABOUT

   KOTLIN
   

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5. 5
   Source: Open Street Map
   

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6. Kotlin
   • Created by JetBrains

   • Mix of object & functional paradigms
   • Static & inferred typing

   • Open source, under Apache 2 license

   • Compilable for Java & JS VM, C, Objective-C
   • Last version: 1.3.4
   6
   

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8. < 17 may 2017
   8
   

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9. Grand’pa Java
   9
   😔
   

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10. 17 may 2017!
    10
    

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11. Kotlin for Android
    11
    😻
    Note: Here is the Kotlin code converted from Java code with Android Studio (a bit dirty!!)
    

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13. KOTLIN/NATIVE
    

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14. Definition
    « Kotlin/Native is a technology for compiling Kotlin code to native
    binaries, which can run without a virtual machine.
    It is an LLVM based backend for the Kotlin compiler and native
    implementation of the Kotlin standard library. »
    14
    Source: kotlinlang.org
    

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15. Kotlin/Native
    • Will not replace legacy frameworks
    • Allows to have bidirectional interop. between Kotlin and
    target code
    ! To mutualize/share source code between platforms
    

    Code common, respect the platform
    15
    

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16. Targets
    • A lot of platforms…
    • … where we cannot have or don’t want VM
    16
    

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17. Targets
    17
    x86
    ARM
    MIPS
    

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18. KOTLIN/NATIVE
    Under the hood
    

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19. Platform libs
    19
    

    POSIX
    Apple frameworks
    W3C DOM
    Win32

    …
    x86
    ARM
    MIPS
    

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20. K/N compilation
    20
    Frontend Backend
    Kotlin/Native
    Compiler
    Kotlin/Native: a part of the Kotlin Multiplatform project
    

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21. K/N compilation
    21
    Intermediate
    Representation
    • Cleaning
    • Devirtualization
    LLVM
    Konan
    

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22. .kt
    22
    

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23. IR
    23
    > kotlinc-native --print_bitcode Program.kt 2>Program.IR
    IR
    

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24. WASM
    24
    IR
    > kotlinc-native -target wasm32 Program.kt

    program.wasm + program.wasm.js
    

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25. .so
    25
    IR
    > kotlinc-native -target android_x64 Program.kt

    program.so
    

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26. .kexe
    26
    IR
    

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27. K/N ON iOS APP
    ReX
    

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28. Use case
    28
    Use case: refactoring with K/N of data model in a 100% Swift TV channels app
    

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29. Tools
    29
    https://kotlinlang.org/docs/tutorials/native/apple-framework.html
    

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30. Source sets
    30
    Possible to define several source sets, with EXPECTed methods and ACTUAL definitions based on targets.
    Project
    libs
    src
    common
    android ios
    expect (class, val…)
    actual (class, val…) actual (class, val…)
    

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31. .h
    31
    .h file for the whole framework
    

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32. K/N ON iOS APP
    Companion object
    Static field
    

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33. 33
    [Kotlin] Use the COMPANION
    

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34. 34
    [.h] Definition of INTERNAL CLASS Companion with INSTANCE METHOD
    

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35. 35
    [Swift] No STATIC method, need to call the COMPANION OBJECT
    

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36. K/N ON iOS APP
    Interface
    Protocol
    

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37. 37
    [Kotlin]
    

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38. 38
    [.h]
    

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39. 39
    [Swift] Must use a Swift CLASS to inherit from the interface!
    

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40. 40
    [Swift] "Non-class type cannot conform to class protocol"… even if Swift STRUCTs are used a lot!
    

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41. K/N ON iOS APP
    Enum
    

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43. 43
    [.h] Polymorphism declared with the super class
    

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44. 44
    [Swift] The Kotlin SCREAMING_SNAKE_CASE convention has ben replaced by the camelCase Swift convention
    

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45. K/N ON iOS APP
    Objects

    Class & struct
    

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46. 46
    [Kotlin]
    

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48. 48
    [Swift] A Kotlin DATA CLASS is converted to a CLASS, not a STRUCT!
    

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49. K/N ON iOS APP
    Generics
    

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50. 50
    [Kotlin] Use of a generic parameter T without condition on it
    

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51. 51
    [.h] A NULLABLE object is used
    

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52. 52
    [Swift] An OPTIONAL ANY object is used, no generic here
    

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53. 53
    [Kotlin] Use of a generic parameter T with 1 condition
    

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54. 54
    [.h] Condition on generic parameter is applied
    

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55. 55
    [Swift] No use of generic on this side, only the TYPE in the Kotlin condition
    

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56. 56
    [Kotlin] Use of a generic parameter T with 2 conditions
    

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57. 57
    [.h] ONLY THE 1st condition in Kotlin is applied, not the 2nd nor both
    

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58. 58
    [Swift] No use of generic on this side, only the TYPE of the 1st condition in Kotlin is used
    

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59. 59
    [Swift] Beware with COMPOSITION: "Conformance of generic class to @objc protocol cannot be in an extension"
    

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60. K/N ON iOS APP
    Exceptions
    

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61. 61
    [Kotlin]
    

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62. 62
    [.h] Polymorphism remains applied in structures definition
    

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63. 63
    [Swift] Exception handling is NOT FULLY implemented with Kotlin/Native 1.3
    

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64. 64
    [Swift] "Exceptions are propagated […] as NSError only if method has or inherits @Throws annotation"
    ( ) Except with kotlin.Error and RuntimeException which are not propagated
    *
    *
    

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65. K/N ON iOS APP
    Usual types
    

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66. Types
    66
    

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67. Types
    67
    

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68. Casting
    68
    Beware with types: CAST may be needed
    

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69. AND?
    

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70. Things to note
    • Kotlin project can be a dependance or a full program
    with a main
    • Platforms libs ensure interoperability
    • A specific environment may be mandatory to compile for
    a specific platform
    70
    

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71. 71
    The standard APIs of the target platform are available as DEPENDENCIES in IntelliJ IDEA
    

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72. 72
    KOTLIN code loading HTML page using a POD and displaying it inside a UITextView of the target from APPLE UIKit
    

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73. Limits
    • Web Assembly / JS
    • No exceptions management
    • No efficient memory management
    • No debugging
    • iOS
    • Beware with the Objective-C layer
    • Some Java APIs are not available
    • java.util.Date, java.math.BigDecimal

    ! Must use platforms libs like POSIX
    73
    

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74. Conclusion
    • K/N interesting for data model or work logic
    • Good integration in iOS projects
    • Gradle’s black magic is helpful (but heavy)
    • Kotlin extensions bring multiplatforms API
    74
    

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75. Ready for production?
    75
    Not today? It seems IceRock and Rekab use Kotlin/Native.
    « This beta version of Kotlin/Native technology is not yet
    tuned for benchmarking and competitive analysis of any kind. »
    GitHub
    

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76. THANK/YOU!
    Questions?
    

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77. RESOURCES
    

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78. To go further
    • Building Multiplatform Projects with Gradle – kotlinlang.org
    • Getting started with Kotlin/Native – sakib.ninja
    • JetBrains / kotlin-native – GitHub
    • JetBrains / kotlin-native / samples – GitHub
    • Kotlin Multiplatform - Medium.com, Mehdi Sohrabi
    • Kotlin on Android. Now official – blog.jetbrains.com, Maxim Shafirov
    • Kotlin/Native + CLANG, travel notes – Nikolai Igotti (JetBrains)
    • Kotlin/Native and Multiplatform – raywenderlich.com
    • Kotlin/Native as an Apple Framework – kotlinlang.org
    • Kotlin/Native interoperability – kotlinlang.org
    • Kotlin/Native interoperability with Swift/Objective-C – kotlin.org
    • LLVM – Chris Lattner
    • My first experience with Kotlin Native – Medium.com, Florent Champigny
    • Plateform-Specific implementations in Kotlin Multiplatform - medium.com, Simone Civetta
    • Targeting iOS and Android with Koltin Multiplatform – play.kotlinlang.og
    • The magic of Kotlin/Native (1, 2, 3) – Medium.com, Vivek Singh
    • What is LLVM? The power behind Swift, Rust, Clang, and more – InfoWorld.com, Serdar Yegulalp
    • Why we need Kotlin/Native - Medium.com, Jeremy Rempel
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79. Credits
    • Native_overview.png – modified with Gimp
    • Capture of Captain America: Civil War – Marvel Studios ; Marvel Entertainment ; Russo Brothers ; Vita-Ray Productions, LLC
    • Bugdroid, la mascotte représentant Android – CC-BY-SA 3.0, Google Inc.
    • Java free icon – Flaticon Basic License, Freepik
    • Hero.svg – modified with Gim
    • Logo de iOS – public domain, Apple Inc.
    • Logo de macOS – public domain, Apple Inc.
    • Logo de watchOS – public domain, Apple Inc.
    • Logo de tvOS – public domain, Apple Inc.
    • Logo de Android – public domain
    • Logo de Windows – public domain
    • Logo de Linux – CC0, Larry Ewing, Simon Budig, Garrett LeSage
    • Logo de Raspberry Pi – Copyright Apache Cordova
    • Logo de Web Assembly – CC0, Carlos Beraza
    • Logo de JavaScript – public domain, Chris Williams
    • Engine free icon – Flaticon Basic License, Flat Icons
    79
    • Binary code free icon – Flaticon Basic License, Freepik
    • Logo de IntelliJ IDEA – public domain, JetBrains
    • Logo de Xcode – Apple
    • Logo de Swift – public domain, modified with Gimp
    • Logo of Gradle
    • Code samples wrapped with Carbon
    • iPhone mockup made with Smartmockups
    • Logo of Code d’Armor – Copyright © Code d’Armor
    • Logo of DevFest du Bout du Monde - Copyright © DevFest du Bout du Monde
    • Logo of Orange – public domain, Cbuckley
    • Logo of DevFest 3019 and wallpaper – Copyright © GDG Strasbourg
    • Memes created with imgflip.com
    In random order
    

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