Kotlin Multiplatform in Production

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Kotlin Multiplatform In Production Kevin Galligan

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Touchlab

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Community community!

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What is Kotlin Multiplatform?

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kot·lin mul·ti·plat·form /ˌkätˈlin məltiˈplatfôrm,ˌkätˈlin məltīˈplatfôrm/ noun noun: kotlin multiplatform 1.optional, natively-integrated, open-source, code sharing platform, based on the popular, modern language kotlin. facilitates non-ui logic availability on many platforms.

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Optional Sharing Low risk. No Big Decisions.

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Natively Integrated smooth interop

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open source

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Code Sharing not “cross platform”

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popular

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popular

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popular

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language & tools

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modern

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Not UI well, not necessarily UI

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Shared UI == Failure!

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Shared Logic == Computers

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Many Platforms

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Kotlin

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Kotlin JVM

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Kotlin JVM JS

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Kotlin JVM JS Native

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Kotlin JVM JS Native iOS Mac Linux Windows Android/NDK Others…

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Kotlin JVM JS Native iOS Mac Linux Windows Android/NDK Others… Webassembly

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Kotlin JVM JS Native iOS Mac Linux Windows Android/NDK Others… Webassembly Many Platforms

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Why Kotlin? High Efficiency Low Risk Modern Language/Tools Highly Engaged Community

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mobile is easy

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mobile is easy

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Status

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Q3 Q2 Q4 Q1 Q2 2018 2019 0 .6 v0.7 v0.8 v0.8.2 v0.9.3 IDE tooling! Coroutines?

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Q3 Q2 Q4 Q1 Q2 2018 2019 0 .6 v0.7 v0.8 v0.8.2 v0.9.3 IDE tooling! Coroutines? K/N 1.0, Kotlin 1.3 Gradle 4.10+ Android Studio

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Q3 Q2 Q4 Q1 Q2 2018 2019 0 .6 v0.7 v0.8 v0.8.2 v0.9.3 IDE tooling! Coroutines? K/N 1.0, Kotlin 1.3 Gradle 4.10+ Android Studio Other samples/libraries Production deployments Compiler plugins! MT Coroutines!

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Q3 Q2 Q4 Q1 Q2 2018 2019 0 .6 v0.7 v0.8 v0.8.2 v0.9.3 IDE tooling! Coroutines? K/N 1.0, Kotlin 1.3 Gradle 4.10+ Android Studio Compiler plugins! Other samples/libraries Production deployments Paid license/debugger Reactive Library Big Production Apps Webassembly stuﬀ? MT Coroutines!

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TL;DR March start getting real end of Q1

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SHARED CODE FOR ANDROID & IOS

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Common

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Common mainThread?

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expect val mainThread:Boolean

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expect val mainThread:Boolean actual val mainThread: Boolean get() = Looper.myLooper() === Looper.getMainLooper()

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expect val mainThread:Boolean actual val mainThread: Boolean get() = Looper.myLooper() === Looper.getMainLooper() actual val mainThread: Boolean get() = NSThread.isMainThread()

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expect val mainThread:Boolean actual val mainThread: Boolean get() = Looper.myLooper() === Looper.getMainLooper() actual val mainThread: Boolean get() = NSThread.isMainThread() actual val mainThread: Boolean = true

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expect fun currentTimeMillis():Long expect fun backgroundTask(backJob:()-> B, mainJob:(B) -> Unit) expect fun backgroundTask(backJob:()->Unit) expect fun networkBackgroundTask(backJob:()->Unit) expect fun initContext():NativeOpenHelperFactory expect fun goFreeze(a:T):T expect fun T.freeze2(): T expect fun simpleGet(url:String):String expect fun logException(t:Throwable) expect fun settingsFactory(): Settings.Factory expect fun createUuid():String

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expect class Date { fun toLongMillis():Long } expect class DateFormatHelper(format:String){ fun toDate(s:String):Date fun format(d:Date):String }

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actual class Date(val date:java.util.Date) { actual fun toLongMillis(): Long = date.time } actual class DateFormatHelper actual constructor(format: String) { val dateFormatter = object : ThreadLocal(){ override fun initialValue(): DateFormat = SimpleDateFormat(format) } actual fun toDate(s: String): Date = Date(dateFormatter.get()!!.parse(s)) actual fun format(d: Date): String = dateFormatter.get()!!.format(d.date) }

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fun initPlatformClient( staticFileLoader: (filePrefix: String, fileType: String) -> String?, analyticsCallback: (name: String, params: Map) -> Unit, clLogCallback: (s: String) -> Unit) {

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fun initPlatformClient( staticFileLoader: (filePrefix: String, fileType: String) -> String?, analyticsCallback: (name: String, params: Map) -> Unit, clLogCallback: (s: String) -> Unit) { AppContext.initPlatformClient ({filePrefix, fileType -> loadAsset("${filePrefix}.${fileType}")}, {name: String, params: Map -> val event = CustomEvent(name) //Loop Answers.getInstance().logCustom(event) }, { Log.w("MainApp", it) })

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let appContext = AppContext() appContext.doInitPlatformClient(staticFileLoader: loadAsset, analyticsCallback: analyticsCallback, clLogCallback: csLog) func loadAsset(filePrefix:String, fileType:String) -> String?{ do{ let bundleFile = Bundle.main.path(forResource: filePrefix, ofType: fileType) return try String(contentsOfFile: bundleFile!) } catch { return nil } }

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Common

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JVM Native Common

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JVM Native Common Framework

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JVM Native Common Framework

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JVM Native Common Android Stuff Framework iOS Stuff

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Libraries!

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Jetbrains • Ktor • Kotlinx.Coroutines • Kotlinx.io • Kotlinx.serialization • Atomic-fu (maybe?)

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Community • Sqldelight • Knarch.db • Multiplatform Settings • Stately • OKIO2 (developing) • Timber (sort of)

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Community • Sqldelight • Knarch.db • Multiplatform Settings • Stately • OKIO2 (developing) • Timber (sort of)

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SQLiter trim, lightly opinionated SQLite driver

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SQLit trim, lightly opinionated SQLite driver

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Targets Native SQLite

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Targets Native SQLite Native SQL Encrypted

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Targets Native SQLite Native SQL Encrypted Android SQLite

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Targets Native SQLite Native SQL Encrypted Android SQLite Android SQL Encrypted

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Targets Native SQLite Native SQL Encrypted Android SQLite Android SQL Encrypted JS?

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Public Service Announcement if you understand anything about native…

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STATE

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3 Ecosystems JVM, JS, and Native

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Kotlin/Native State Rules

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Rule #1 Live state belongs to 1 thread

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Rule #2 Frozen state can be shared by threads

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No threading primitives No “synchronized”, “volatile”, etc

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Runtime Safety Kotlin/Native can verify safe mutability

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JVM/JS? See Kotlinconf keynote

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Short term pain Tradeoff for future

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How does Kotlin know?!

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FROZEN!

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FROZEN!

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Runtime Designation AKA a flag

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Call freeze()

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One-way operation No unfreeze()

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class TalkExamples{ var justCountingStuff:Int = 0 init { backgroundCall { //do something justCountingStuff++ }.freeze() } }

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class TalkExamples{ var justCountingStuff:Int = 0 init { backgroundCall { //do something justCountingStuff++ }.freeze() } }

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Usually OK Data objects should be immutable

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Global state more difficult Service object, large memory state

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Passing State

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DetachedObjectGraph(TransferMode.SAFE) { ListData("asdf") }

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val data = ListData("asdf") DetachedObjectGraph(TransferMode.SAFE) { data }

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private val stateBox: AtomicReference> = AtomicReference( DetachedObjectGraph(mode = TransferMode.SAFE, producer = { mutableListOf() as Any }) ) private val lock = NSLock() internal fun withLockDetached(proc: (MutableList) -> MutableList) { lock.lock() try { stateBox.value = DetachedObjectGraph(mode = TransferMode.SAFE, producer = { val dataList = stateBox.value.attach() as MutableList proc(dataList) as Any }) } finally { lock.unlock() } }

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Detaching Time must visit whole graph

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Atomics! Mutable immutable

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AtomicInt/AtomicLong

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AtomicReference Update with frozen objects

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val lambdas = AtomicReference(null) fun initPlatformClient( staticFileLoader: (filePrefix: String, fileType: String) -> String?, analyticsCallback: (name: String, params: Map) -> Unit, clLogCallback: (s: String) -> Unit) { lambdas.value = PlatformLambdas( staticFileLoader, analyticsCallback, clLogCallback).freeze() }

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Stately! v0.3.1~ish

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Multiplatform Definitions • freeze() method and frozen info • Atomics (Int, Long, Reference) • K/N state-related annotations (@ThreadLocal/ @SharedImmutable) • Shared Collections!

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More Info and Tutorials https://github.com/touchlab/KotlinMultiplatformStuff

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Making a Library! a very small library

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Download Intellij EAP https://www.jetbrains.com/idea/nextversion/

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targets { fromPreset(presets.jvm, 'jvm') // This preset is for iPhone emulator // Switch here to presets.iosArm64 to build library for iPhone device fromPreset(presets.iosX64, 'ios') { compilations.main.outputKinds('FRAMEWORK') } }

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targets { fromPreset(presets.jvm, 'jvm') // This preset is for iPhone emulator // Switch here to presets.iosArm64 to build library for iPhone device fromPreset(presets.macosX64, 'ios') /*{ compilations.main.outputKinds('FRAMEWORK') }*/ }

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targets { fromPreset(presets.jvm, 'jvm') fromPreset(presets.js, 'js') fromPreset(presets.macosX64, 'macos') fromPreset(presets.iosX64, 'iosX64') fromPreset(presets.iosArm32, 'iosArm32') fromPreset(presets.iosArm64, 'iosArm64') }

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Live Coding is a Bad Idea don’t be a hero

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Go to Github https://github.com/kpgalligan/MyNewLibrary

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Much More obviously

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Libraries Needed • File Access • Date (310 port) • Mocking (and other test support) • Reactive • UI State

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Getting Started

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Join Kotlin Slack https://slack.kotlinlang.org

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Sample Apps the conference apps

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https://github.com/touchlab/DroidconKotlin/

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Sample Libraries Stately SQLDelight

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Office Hours - Kotlin Multiplatform 2pm in Coblenz

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kevin@touchlab.co @kpgalligan

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kevin@touchlab.co @kpgalligan Join the team !