Kotlin/Native for Multiplatform development

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Kotlin/Native for Multiplatform Development Enrique López Mañas Google Developer Expert

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Ego Slide • Freelance Dev • Google Developer Expert • @eenriquelopez

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Multiplatform development < Costs Sharing code within the company Feature teams > Quality

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Multiplatform development Platform Proprietary Hybrid HTML & JavaScript Frameworks Cross-platform Native

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Kotlin Modern language

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Kotlin Interop

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Kotlin Community support

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Kotlin Top-notch tooling

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Kotlin Sharing is optional! No life or death commitment

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Current situation Q2 Q3 Q4 Q1 Q2 v0.7 v0.8 v0.8.2 v0.9.3

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Kotlin/Anywhere Android Browser Server

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Kotlin/Native Common JVM Native iOS framework Your iOS dev Your Android Dev JS

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Kotlin/Native Sharing architecture (not UI) Shared UI is a mess

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Kotlin/Native - Uses LLVM (5.0) - Provides runtime guarantees - Exceptions, memory management - Interop with C/Objective-C (Swift) - Platform libraries (POSIX, Apple Frameworks, Win32, DOM, etc)

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Kotlin/Native Kotlin Compiler LLVM Kotlin Source Code (.kt) Platform Binary IR

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The compiler -Shares Front-end with Kotlin/JVM and Kotlin/JS - Written in Java and Kotlin - Produces bitcode via LLVM API

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Memory Management - ARC with Cycle Collector - When working pure Kotlin,don’t worry about memory management - Weak references supported - Memory sharing model - Different threads have disjoint object graphs - Object subgraphs can be transferred between threads - Immutable objects can be shared

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Interoperatibility - Interoperatibility with C, Objective-C and Swift - Kotlin can call C/Objective-C and vice-versa - Kotlin can extend Objective-C classes and vice-versa - Memory management aware of Objective-C runtime

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Mapping - Numbers are kept - Strings converted - Kotlin declarations wrapping C entities (functions, struct, unions, etc.) are auto- generated - Objective-C OO concepts (classes, protocols, blocks) are represented as matching Kotlin entities (classes interfaces, lambdas) - For Objective-C, Kotlin code can be compiled to a framework

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Kotlin Library - Hold collection of code for reusability and sharing - Own format: ‘klib’ extension, which holds metadata and bitcode - Tool for creating and storing libraries in repositories

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Existing native libraries - Ktor - Kotlinx.Coroutines - Kotlinx.io - Atomic-fu

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Community projects - Sqldelight - Knarch.db - Multiplatform settings - Stately - OKIO2 (under development)

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expect/actual

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expect/actual

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expect/actual

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expect/actual JVM

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expect/actual JS

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Considerations in state An object belongs to one thread

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Considerations in state Frozen objects can be shared by threads

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Considerations in state No threading primitives: synchronized, volatile Use atomic-fu instead

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Considerations in state Runtime safety: Kotlin/Native can verify safe mutability

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Concurrency - frozen objects Everything you have written until now is not frozen

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Get started git clone https://github.com/JetBrains/kotlin-native ./gradlew dependencies:update ./gradlew bundle kotlinc hello.kt -o hello -opt

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The future Hard to make predictions, easier to bet safe “I don’t know what will happen in 10 years, but there will be people asking in SO about regular expressions, and there will be another JS framework ”

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Flutter vs Kotlin/Native? Flutter - custom UI Widgets Dart - better Threading support Kotlin - more performant Kotlin - better ecosystem

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Recommendations - Use it with caution - Shared components - Keep versioning in mind - Do not compromise 100% of a project

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Further resources Kotlin Slack (kotlinlang.slack.com) Touchlab resources (https://github.com/touchlab) Kotlin Weekly (http://kotlinweekly.net) K/N documentation (https://kotlinlang.org/docs/ reference/native-overview.html)

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