Kotlin Multiplatform Architecture

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Kotlin Multiplatform Architecture Kevin Galligan

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Touchlab

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Community community!

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SHARED ARHICTECTURE

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Mobile & Web Architecture, not UI

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Shared UI == Failure!

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Shared Loigc == Computers

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Web is more difficult No SQL :(

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Advocate for new standards I want SQL again

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https://hacks.mozilla.org/

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mobile is MUCH simpler

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Why Kotlin?

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Modern Language

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Community Excitement

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Best Tools

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Smooth Interop

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Optional Sharing Low risk. No Big Decisions.

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“Everything Should Be Made as Simple as Possible, But Not Simpler” - Albert Einstein Maybe?

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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 MT Coroutines! Other samples/libraries Production deployments

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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 MT Coroutines! Other samples/libraries Production deployments Paid license/debugger Reactive Library Big Production Apps Webassembly stuﬀ?

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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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JVM Native Common

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JVM Native Common Ktor-JVM Ktor-Native Ktor

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

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DROIDCON WITH KOTLIN MULTIPLATFORM

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Funky Code Testbed

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Funky Code Testbed Kotlin in 2014!

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Droidcon NYC & SF

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SQLite Knarch.db Android iOS

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SQLite Knarch.db SQLDelight Android iOS

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SQLite Knarch.db SQLDelight Logic! Reactive (LiveData) Android iOS

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SQLite Knarch.db SQLDelight Logic! Reactive (LiveData) Android iOS

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SQLite Knarch.db SQLDelight MP Settings Logic! Reactive (LiveData) Android iOS

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val evenLiveData:EventLiveData init { val query = goFreeze(AppContext.dbHelper. queryWrapper.sessionQueries. sessionById(sessionId)) evenLiveData = EventLiveData(query) } fun shutDown(){ evenLiveData.removeListener() }

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override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? { eventViewModel.eventModel.evenLiveData. observe(viewLifecycleOwner, Observer { dataRefresh(it) }) return initView(inflater, container) }

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fun registerForChanges(proc:(sessionInfo:SessionInfo)->Unit){ eventObserver = object : Observer{ override fun onChanged(t: SessionInfo?){ if(t != null) proc(t) } } eventModel.evenLiveData.observeForever(eventObserver!!) }

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viewModel = EventViewModel(sessionId: sessionId) viewModel.registerForChanges(proc: updateUi)

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viewModel = EventViewModel(sessionId: sessionId) viewModel.registerForChanges(proc: updateUi) func updateUi(sessionInfo:SessionInfo) -> KotlinUnit{ self.sessionInfo = sessionInfo styleButton() updateAllUi() return KotlinUnit() }

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Droidcon App Kotlin Multiplatform https://www.youtube.com/watch?v=YAeDK3Ei0Lk https://github.com/touchlab/DroidconKotlin/ Now with 0.9.3!

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KOTLINCONF WITH KOTLIN MULTIPLATFORM (OBV)

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Settings Android iOS Ktor

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Settings Android iOS Ktor DataRepository

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Settings Android iOS Ktor DataRepository SessionDetailsPresenter

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Settings Android iOS Ktor DataRepository SessionDetailsPresenter SessionDetailsView

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interface SessionDetailsView : BaseView { fun updateView(isFavorite: Boolean, session: SessionModel) fun setupRatingButtons(rating: SessionRating?) fun setRatingClickable(clickable: Boolean) } override fun updateView(isFavorite: Boolean, session: SessionModel) { collapsingToolbar.title = session.title speakersTextView.text = session.speakers.joinToString(separator = ", ") { it.fullName } timeTextView.text = session.timeString detailsTextView.text = listOfNotNull(session.roomText, session.category).joinToString(", ") descriptionTextView.text = session.descriptionText val online = context?.let { it.isConnected?.and(!it.isAirplaneModeOn) } ?: false for (button in listOf(votingButtonsLayout, favoriteButton)) { func updateView(isFavorite: Bool, session: SessionModel) { titleLabel.text = session.title let startsAt = session.startsAt let endsAt = session.endsAt if (startsAt != nil && endsAt != nil) { timeLabel.text = KotlinPair(first: startsAt, second: endsAt).toReadableString() } let image = UIImage(named: isFavorite ? "star_full" : "star_empty")! favoriteButton.image = image

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Settings Android iOS Ktor DataRepository SessionDetailsPresenter SessionDetailsView

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KotlinConf App https://github.com/JetBrains/kotlinconf-app

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Which?

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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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all the code you’ve ever written not frozen frozen

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all the code you’ve ever written not frozen frozen

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One-way operation No unfreeze()

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Freezes everything

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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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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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data class FrozenData( val someCount:AtomicInt, val someString:String, val someOtherState:AtomicReference ) data class OtherState( val otherCount:Int, val otherString:String )

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val frozenData = FrozenData( AtomicInt(1), "asdf", AtomicReference( OtherState( 1, "qwert") ) ).freeze()

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val frozenData = FrozenData( AtomicInt(1), "asdf", AtomicReference( OtherState( 1, "qwert") ) ).freeze()

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fun update(frozenData: FrozenData){ frozenData.someCount.increment() val otherState = frozenData.someOtherState.value val updated = otherState.copy(otherCount = otherState.otherCount+1) frozenData.someOtherState.value = updated.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)

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Multithreaded Collections Built on atomics

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val cowList = frozenCopyOnWriteList() val sharedList = frozenLinkedList() val coiSharedList = frozenLinkedList(stableIterator = true) val sharedMap = frozenHashMap() val lruRemovedCount = AtomicInt(0) val lruCache = frozenLruCache(5) { lruRemovedCount.increment() }

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Why? If you have to ask…

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Changing Architectures Coroutines, libraries, best practices

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THREADING

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Workers like Executor

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Passing State similar to DetachedObjectGraph

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Until Coroutines MT coroutines will largely replace Worker

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Coroutines and State? we’ll see

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LIBRARIES

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Jetbrains • Ktor • Kotlinx.Coroutines • Kotlinx.io • Atomic-fu

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