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

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

KOTLIN NATIVE

ABOUT
 KOTLIN

5 Source: Open Street Map

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

7

< 17 may 2017 8

Grand’pa Java 9 😔

17 may 2017! 10

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

12

KOTLIN/NATIVE

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

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

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

Targets 17 x86 ARM MIPS

KOTLIN/NATIVE Under the hood

Platform libs 19 
 POSIX Apple frameworks W3C DOM Win32
 … x86 ARM MIPS

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

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

.kt 22

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

WASM 24 IR > kotlinc-native -target wasm32 Program.kt
 program.wasm + program.wasm.js

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

.kexe 26 IR

K/N ON iOS APP ReX

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

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

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…)

.h 31 .h file for the whole framework

K/N ON iOS APP Companion object Static field

33 [Kotlin] Use the COMPANION

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

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

K/N ON iOS APP Interface Protocol

37 [Kotlin]

38 [.h]

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

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

K/N ON iOS APP Enum

42

43 [.h] Polymorphism declared with the super class

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

K/N ON iOS APP Objects
 Class & struct

46 [Kotlin]

47

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

K/N ON iOS APP Generics

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

51 [.h] A NULLABLE object is used

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

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

54 [.h] Condition on generic parameter is applied

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

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

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

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

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

K/N ON iOS APP Exceptions

61 [Kotlin]

62 [.h] Polymorphism remains applied in structures definition

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

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 * *

K/N ON iOS APP Usual types

Types 66

Types 67

Casting 68 Beware with types: CAST may be needed

AND?

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

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

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

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

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

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

THANK/YOU! Questions?

RESOURCES

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 78

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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