SHIPPING MULTIPLATFORM ON IOS & ANDROID BEN ASHER ALEC STRONG - PowerPoint PPT Presentation

SHIPPING MULTIPLATFORM ON IOS & ANDROID BEN ASHER ALEC STRONG @benasher44 @strongolopolis Copenhagen Denmark

SHIPPING MULTIPLATFORM ON IOS & ANDROID BEN ASHER ALEC STRONG @benasher44 @strongolopolis Copenhagen Denmark

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Championed on iOS Championed on Android ~15 across Android and iOS ~30 across Android and iOS Construction Financial Services

Offline Search Sync System Business Logic

Business Logic Models

MPP Business Logic Models

MPP Business Logic Models

MPP

MPP Kotlin/Native

New tools 🌯🌯🌯 New language 🌯🌯🌯 Uneven ecosystem

Adopting cross-platform in your app has a cost

What is the value that makes it worth the effort?

Diverging Sync Systems

Existing Shared Code

What tools will your cross-platform solution need What is the common goal all stakeholders have

What else? No JNI on Android Obj-C 
 Community Interop Not New Jetbrains For Android

Common Questions Kotlin/Native relies on Obj-C? What about Swift? Obj-C header is well-annotated for Swift This is the status quo for Apple’s own frameworks

Common Questions What about performance? Same performance expectations on Android Can drop into C if needed on iOS

Common Questions What about value types?

Common Questions There’s a garbage collector? But there’s no JVM, right? Bacon’s Algorithm for GC

Common Questions What libraries can we use for mpp? JVM Distributions are incomplete Special multiplatform distributions K/N ABI instability (klib)

Common Questions What is “common” code?

Library Outputs Library Source Sets iosMain iOS - .framework commonMain Android - .aar androidMain

Library Outputs Library Source Sets Code actual class Lock iosMain iOS - .framework expect class Lock commonMain Android - .aar actual class Lock androidMain

Library Outputs Library Source Sets actual class Lock iosMain iOS - .framework commonMain expect class Lock Android - .aar androidMain actual class Lock

Library Outputs Library Source Sets iosMain iOS - .framework commonMain Android - .aar androidMain

Library Outputs Library Source Sets iosMain iOS - .framework commonMain Android - .aar androidMain

Library Outputs Library Source Sets iosMain iOS - .framework commonMain Android - .aar androidMain Windows - .dll windowsMain

commonMain Yes Platform Yes Is it platform agnostic? No Will other common No code use it?

commonMain Yes Platform Yes Is it platform agnostic? No Will other common No code use it?

commonMain Yes Is it platform agnostic? Will other common No code use it?

expect class DatabaseFactory { internal fun createSqliteDriver(): SqlDriver }

Platform Is it platform agnostic? No Will other common No code use it?

sourceSets {A commonMain {B}C androidLibMain {D}E iosLibMain {F}G }H

sourceSets {A commonMain {B}C androidLibMain {D dependencies {I api project(‘:protos') }J }E iosLibMain {F}G }H

fun SearchQueries.insert(entity: SyncEntity) entity: SyncEntity

sourceSets {A commonMain {B}C androidLibMain {D}E iosLibMain {F}G }H

sourceSets {A commonMain {B}C androidLibMain {D}E }H

commonMain Yes Is it platform agnostic?

fun search(terms: String): List<Search>?

Library Source Sets iosMain Host 
 commonMain Application androidMain

Host 
 Application Talks to backend API Talks to existing application state

Library Initialization Host 
 commonMain Application Library defines interface App provides implementation

Case Study: Networking Highly platform-specific Backend API Hosts Current user’s credential

MPP Life Hack: Interface Network Make an API request Receive an async response Interface can be re-implemented later

interface Network { /** * Makes an API request */ fun makeRequest( host: APIHost, request: Request, completion: (Request.Response) -> Unit ): NetworkDisposable }

interface Network { /** * Makes an API request */ fun makeRequest( host: APIHost, host: APIHost request: Request, completion: (Request.Response) -> Unit ): NetworkDisposable } Plain enum of names of the hosts– no URL handling required

data class: interface Network { - String path and body, /** * Makes an API request - query params dict */ fun makeRequest( - enum method (GET, POST, etc.) host: APIHost, request: Request, request: Request completion: (Request.Response) -> Unit ): NetworkDisposable }

interface Network { /** * Makes an API request */ fun makeRequest( host: APIHost, request: Request, completion: (Request.Response) -> Unit completion: (Request.Response) -> Unit ): NetworkDisposable } sealed class w/ different response types:

interface Network { /** * Makes an API request */ fun makeRequest( host: APIHost, request: Request, completion: (Request.Response) -> Unit ): NetworkDisposable NetworkDisposable } Interface with a cancel() method

suspend fun Network.makeRequest( host: APIHost, request: Request ): Request.Response

Concurrency in commonMain actual fun <T> T.freeze(): T = freeze() iosMain expect fun <T> T.freeze(): T commonMain actual fun <T> T.freeze(): T = this androidMain

Shipping Internally iosMain Host 
 commonMain Application androidMain

iosMain Host 
 Host 
 commonMain Application Application androidMain

iosMain Host 
 Host 
 commonMain Application Application androidMain

Pros Cons Minimal change for android Two build environments for iOS Seamless local development CI Nightmare Single source of truth Host dependencies

iosMain Host 
 Host 
 commonMain Application Application androidMain

iosMain Host 
 Host 
 commonMain Application Application androidMain

iosMain Host 
 Host 
 commonMain commonMain Application Application androidMain

Host 
 Host 
 Application Application commonMain commonMain androidMain iosMain

Pros Cons Minimal change for android Two build environments for iOS Seamless local development CI Nightmare for iOS Host dependencies Out of sync code

iosMain Host 
 Host 
 commonMain Application Application androidMain

Host 
 Host 
 Application Application iosMain commonMain androidMain

Pros Cons Breaking changes are painful CI is fast Need good CD setup Encourages unit test coverage Debugging decoupled repos Single source of truth

iosMain Host 
 Host 
 commonMain Application Application androidMain

iosMain Host 
 Host 
 Application Application commonMain androidMain

commonMain Host 
 Host 
 Application Application androidMain

Shipping Externally Test Crashing!

Shipping Externally fun crash() { (null as String?)!! }

Shipping Externally setUnhandledExceptionHook()

Shipping Externally What happens if a Worker crashes?

Review Define your project’s goals Be thoughtful growing your codebase Avoid solving general muliplatform problems Get your CI and dev setup working early Join us in Kotlin slack

THANK YOU AND REMEMBER TO VOTE Ben Asher @benasher44 Alec Strong @Strongolopolis #KotlinConf