I Walk The Line - What Should Be Kotlin/Native And What (Maybe) Shouldn't - KotlinConf, Copenhagen, Denmark, December 2019

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I WALK THE LINE WHAT SHOULD BE KOTLIN/NATIVE, AND WHAT (MAYBE) SHOULDN'T KOTLINCONF | COPENHAGEN, DENMARK | DECEMBER 2019 ELLEN SHAPIRO | @DESIGNATEDNERD | APOLLOGRAPHQL.COM

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EVERYONE HAS A CROSS-PLATFORM ! HORROR STORY

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! AIRBNB : REACT NATIVE

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JAVASCRIIIIIIIIPT!

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! DROPBOX C++

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DE-PRIORITIZE DEVELOPER EXPERIENCE AT YOUR OWN RISK

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DEVS WHO HAVE WORKED IN SAFER LANGUAGES REFUSE TO GO BACK

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! SHAMELESS PLUG ALERT!

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KOTLIN/NATIVE FOCUSES ON SHARING LOGIC

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CENTRALIZE TESTING

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USE KOTLIN/NATIVE FOR ALL THE THINGS!

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! PORCH PIRATE PROTECTOR https://github.com/bakkenbaeck/porchpirateprotector

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iOS app

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iOS app Android app

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iOS app Android App Server

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iOS app Android app Server Raspberry pi

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Works With Kotlin? iOS app Android app Server Raspberry pi

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Works With Kotlin? iOS app ✅ Android app ✅ Server ✅ Raspberry pi ✅

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Works With Kotlin? iOS app ✅ Android app ✅ Server ✅ Raspberry pi* ✅ * - soon, I hope

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MVA*

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MVA* * - ANYTHING OTHER THAN A MODEL OR A VIEW FOR THE LOVE OF GOD

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MVP

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MODEL: VIEW: PRESENTER:

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MODEL: data class VIEW: PRESENTER:

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MODEL: data class VIEW: interface PRESENTER:

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MODEL: data class VIEW: interface PRESENTER: class

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VIEW: interface

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IOS VIEW: UIViewController ANDROID VIEW: TESTING VIEW:

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IOS VIEW: UIViewController ANDROID VIEW: Fragment* TESTING VIEW:

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IOS VIEW: UIViewController ANDROID VIEW: Fragment* TESTING VIEW: *May not apply if your name is jake wharton

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IOS VIEW: UIViewController ANDROID VIEW: Fragment* TESTING VIEW: ¯\_(ϑ)_/¯ *May not apply if your name is jake wharton

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commonMain PRESENTER class DeviceDetailPresenter( val view: DeviceDetailView, val device: PairedDevice, storage: SecureStorage ): BaseCoroutinePresenter(secureStorage = storage) { // ... }

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commonMain VIEW interface DeviceDetailView: IndefiniteLoadingIndicating { fun setTitle(toString: String) fun setLockButtonEnabled(enabled: Boolean) fun setUnlockButtonEnabled(enabled: Boolean) fun setApiError(toString: String?) }

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ANDROID APP FRAGMENT class DeviceDetailFragment: Fragment(), DeviceDetailView { private val presenter by lazy { DeviceDetailPresenter( this, currentDevice, KeyStoreManager(this.context!!) ) } //... }

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WHAT HAVE I DONE WRONG HERE? class DeviceDetailFragment: Fragment(), DeviceDetailView { private val presenter by lazy { DeviceDetailPresenter( this, currentDevice, KeyStoreManager(this.context!!) ) } //... }

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PRESENTER class DeviceDetailPresenter( val view: DeviceDetailView, val device: PairedDevice, storage: SecureStorage ): BaseCoroutinePresenter(secureStorage = storage) { // ... }

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(Copyright Alex Norris of Webcomic Name)

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MVP

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MVSP

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MVSP MODEL VIEWSTATE PRESENTER

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VIEW INTERFACES -> VIEWSTATE OBJECTS

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class DeviceDetailPresenter( val device: PairedDevice ): BaseCoroutinePresenter() { data class DeviceDetailViewState( val lockButtonEnabled: Boolean, val unlockButtonEnabled: Boolean, val errorMessage: String? = null, val indicatorAnimating: Boolean = false ) // ... }

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suspend fun getStatusAsync( initialViewStateHandler: (DeviceDetailViewState) -> Unit, secureStorage: SecureStorage ): DeviceDetailViewState { // ... } suspend fun lockAsync( initialViewStateHandler: (DeviceDetailViewState) -> Unit, secureStorage: SecureStorage ): DeviceDetailViewState { //... } suspend fun unlockAsync( initialViewStateHandler: (DeviceDetailViewState) -> Unit, secureStorage: SecureStorage ): DeviceDetailViewState { //.. }

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UNIDIRECTIONAL ♻ DATA FLOW

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BLAME SWIFTUI

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DESTROY YOUR HEROES UI STATE

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import SwiftUI struct ValueView: View { var value: Double = 0 var body: some View { return Text("\(value)") } }

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import SwiftUI struct ValueView: View { var value: Double = 0 var body: some View { return Text("\(value)") } }

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import SwiftUI struct ValueView: View { var value: Double = 0 var body: some View { return Text("\(value)") } }

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LESS MUTABLE STATE -> FEWER PROBLEMS

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SHARING MAKES SENSE THEORETICALLY

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STYLE DEFINITION

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COLORS

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val colorPrimary = "#05C1FD" val colorPrimaryDark = "#5848F4" val colorAccent = "#fb5502" val colorAccentSelected = "#c94402" val textLight = "#ffffff" val textMiddle = "#777777" val textDark = "#000000" val errorRed = "#cc0000" val success = "#0d9b2a"

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enum class PPPColor(val hexColor: String) { ColorPrimary("#05C1FD"), ColorPrimaryDark("#5848F4"), ColorAccent("#fb5502"), ColorAccentSelected("#c94402"), TextLight("#ffffff"), TextMiddle("#777777"), TextDark("#000000"), ErrorRed("#cc0000"), Success("#0d9b2a"); val red: Long get() = hexColor.substring(1, 3).toLong(16) val green: Long get() = hexColor.substring(3, 5).toLong(16) val blue: Long get() = hexColor.substring(5, 7).toLong(16) }

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import platform.UIKit.UIColor fun PPPColor.toUIColor(): UIColor { return UIColor( red = this.red.toDouble() / 255.0f, green = this.green.toDouble() / 255.0f, blue = this.blue.toDouble() / 255.0f, alpha = 1.0 ) }

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import android.graphics.Color import no.bakkenbaeck.pppshared.ui.PPPColor fun PPPColor.toAndroidColor(): Int { return Color.parseColor(this.hexColor) }

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SHOULD YOU SHARE CODE OR SOMETHING ELSE?

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! LIBRARIES

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ktor + kotlinx.serialization

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NETWORK + PARSING

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NETWORK + PARSING IOS + ANDROID + SERVER

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@Serializable data class LockState( val deviceId: Int, val isLocked: Boolean )

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KTOR USES SINGLE-THREADED COROUTINES

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DIG IN TO FIND OUT WHERE LIBRARIES ARE KINDA CHEATING

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DATABASE SQLDelight

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PRO: ONE DATABASE TO ! RULE THEM ALL

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CON: GIVE UP DEEP INTEGRATION OF CoreData AND Room

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(HOW BAD IS THAT, REALLY?)

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ANDROID: SQLDELIGHT FLOW EXTENSIONS

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IOS: SWIFTUI

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KNOW WHY YOU'RE USING KOTLIN/NATIVE

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via http://www.dorkly.com/post/67855/watch-someone-beat-all-4-original-mario-games-at-the-same-time

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CROSS-PLATFORM IS NOT AN EXCUSE TO IGNORE THE PLATFORM

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WHAT AM I GIVING UP THAT THE SYSTEM HAS BEEN DOING FOR ME?

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IS IT WORTH THAT TRADE-OFF?

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OBLIGATORY SUMMARY SLIDE

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OBLIGATORY SUMMARY SLIDE > Kotlin/Native can be a double-edged sword

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OBLIGATORY SUMMARY SLIDE > Kotlin/Native can be a double-edged sword > You can move way faster on some things

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OBLIGATORY SUMMARY SLIDE > Kotlin/Native can be a double-edged sword > You can move way faster on some things > Be mindful of the trade-offs you're making

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OBLIGATORY SUMMARY SLIDE > Kotlin/Native can be a double-edged sword > You can move way faster on some things > Be mindful of the trade-offs you're making > Prioritize developer experience to drive adoption

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LINKS! > The (not so) hidden cost of sharing code between iOS and Android https://blogs.dropbox.com/tech/2019/08/ the-not-so-hidden-cost-of-sharing-code- between-ios-and-android/ > React Native at AirBnB https://medium.com/airbnb-engineering/ react-native-at-airbnb-f95aa460be1c