Meet Kotlin Multiplatform Mobile

Presentation from Kotlin Dev Day Amsterdam 2022

Transcript

1. Meet Kotlin Multiplatform Mobile KMM for short Piotr Prus Mobile Tech Lead @Airly GDG 3City Organizer
2. Questions I will try to answer - What is the difference between KMM and other multiplatform solutions like a fl utter, react native, etc? - Is this a good solution for your business and why we thought it is a good decision for us? - How does iOS read the shared module? - How much code can we actually share? - What are the most important libraries and what these are doing? - Is KMM production ready? - Pros and cons of KMM
3. Cross-platform mobile framework popularity Source: www.statista.com, July 2021
4. Cross-platform mobile framework popularity Source: www.statista.com, July 2021
5. Google trends
6. Share code jvm Android iOS Linux macOS Windows JS watchOS tvOS
7. KMM vs KMP First Multiplatform Kotlin 1.2 November 2017 Announced August 2020
8. Why we choose KMM • Small team • Business logic in one place • Promote DDD • iOS needed refactor
9. KMM, the PoC • Con fi guration is tricky, but manageable • Things that works on android, do not need to work on iOS • One repo vs 3 repos • iOS simulator != iOS real device • Sample project != big project 1 week 🎉
10. Networking October 2021
11. Networking January 2022 Persistance Models
12. Networking March 2022 Persistance Models Repositories UseCases
13. Networking June/July 2022 Persistance Models Repositories UseCases ViewModels
14. Networking June/July 2022 Persistance Models Repositories UseCases ViewModels UI layer
15. Share code Domain Repositories Persistance Networking ViewModels Presentation Business(Kotlin) Framework(iOS, Android)
16. KMM libraries 137 libraries KTOR KOIN SQLdelight Multiplatform settings kotlinx.serialization kotlinx.datetime BuildKon fi g Moko-resources
17. Networking with KTOR • open-source • lightweight • powered by coroutines • Build by JetBrains
18. Networking with KTOR fun createHttpClient(httpClientEngine: HttpClientEngine, logger: Logger) = HttpClient(httpClientEngine) { defaultRequest { url.protocol = URLProtocol.HTTP S url.host = BuildKonfig.BASE_UR L parameter("apikey", BuildKonfig.API_KEY ) parameter("Accept-Language", languageCode ?: "en" ) } install(ContentNegotiation) { json(json) } install(Logging) { this.logger = logge r level = logLeve l } }
19. Networking with KTOR fun createHttpClient(httpClientEngine: HttpClientEngine, logger: Logger) = HttpClient(httpClientEngine) { defaultRequest { url.protocol = URLProtocol.HTTP S url.host = BuildKonfig.BASE_UR L parameter("apikey", BuildKonfig.API_KEY ) parameter("Accept-Language", languageCode ?: "en" ) } install(ContentNegotiation) { json(json) } install(Logging) { this.logger = logge r level = logLeve l } } OkHttp + Retro fi t Retro fi t.Builder().baseUrl() In interceptor: chain.request().header()
20. Networking with KTOR fun createHttpClient(httpClientEngine: HttpClientEngine, logger: Logger) = HttpClient(httpClientEngine) { defaultRequest { url.protocol = URLProtocol.HTTP S url.host = BuildKonfig.BASE_UR L parameter("apikey", BuildKonfig.API_KEY ) parameter("Accept-Language", languageCode ?: "en" ) } install(ContentNegotiation) { json(json) } install(Logging) { this.logger = logge r level = logLeve l } } OkHttp + Retro fi t Retro fi t.Builder().baseUrl() In interceptor: chain.request().header() .addConverterFactory(jsonConverter)
21. Networking with KTOR fun createHttpClient(httpClientEngine: HttpClientEngine, logger: Logger) = HttpClient(httpClientEngine) { defaultRequest { url.protocol = URLProtocol.HTTP S url.host = BuildKonfig.BASE_UR L parameter("apikey", BuildKonfig.API_KEY ) parameter("Accept-Language", languageCode ?: "en" ) } install(ContentNegotiation) { json(json) } install(Logging) { this.logger = logge r level = logLeve l } } OkHttp + Retro fi t Retro fi t.Builder().baseUrl() In interceptor: chain.request().header() .addConverterFactory(jsonConverter) .addInterceptor(httpLoggingInterceptor)
22. Http Client Engine Networking with KTOR Android.create() val logger = object : Logger { override fun log(message: String) { Log.i(tag, message) } } Darwin.create() Logger.DEFAULT Logger
23. Actual/Expected
24. Actual/Expected //commo n expect val httpEngine: HttpClientEngin e expect val logger: Logger //androidMai n actual val httpEngine = Android.create( ) actual val logger = object : Logger { override fun log(message: String) { Log.i(tag, message ) } } //iosMai n actual val httpEngine = Darwin.create( ) actual val logger = Logger.DEFAULT
25. iOS and coroutines
26. iOS and coroutines Async/Await RxSwift Combine Callbacks
27. iOS Source: https://dev.to/touchlab/kotlin-coroutines-and-swift-revisited-j5h func createPublisher<T>(flowAdapter: FlowAdapter<T>) -> AnyPublisher<T, KotlinError> { return Deferred<Publishers.HandleEvents<PassthroughSubject<T, KotlinError>>> { let subject = PassthroughSubject<T, KotlinError>( ) let job = flowAdapter.subscribe ( onEvent: { (item) in let _ = subject.send(item) } , onError: { (error) in subject.send(completion: .failure(KotlinError(error))) } , onComplete: { subject.send(completion: .finished) } ) return subject.handleEvents(receiveCancel: { job.cancel(cause: nil ) } ) }.eraseToAnyPublisher( ) }
28. Shared iOS class FlowAdapter<T : Any> ( private val scope: CoroutineScope , private val flow: Flow<T > ) { fun subscribe ( onEvent: (T) -> Unit , onError: (Throwable) -> Unit , onComplete: () -> Uni t ): Job = flo w .onEach { onEvent(it) } .catch { onError(it) } .onCompletion { onComplete() } .launchIn(scope ) }
29. SSOT for resources
30. Resources Moko-resources https://github.com/icerockdev/moko-resources
31. Strings.xml Resources <string name="cancel">Cancel</string > <string name="current_location_widget_label">Current location</string > <string name="date_yesterday">Yesterday</string >
32. Compose Resources stringResource(id = SharedRes.strings.my_string.resourceId) Swift/SwiftUI let string = MR.strings().my_string.desc().localized( ) LocalizedStringKey(MR.strings().email.resourceId)
33. Resources Common val stringDesc = StringDesc.Resource(SharedRes.strings.airlypedia_title)
34. Resources Common val stringDesc = StringDesc.Resource(SharedRes.strings.airlypedia_title) .toString(context)
35. Resources Common val stringDesc = StringDesc.Resource(SharedRes.strings.airlypedia_title) .toString(context) .localized()
36. Resources Common val stringDesc = StringDesc.Resource(SharedRes.strings.airlypedia_title ) expect fun ResourceStringDesc.getText(): String
37. Resources Common val stringDesc = StringDesc.Resource(SharedRes.strings.airlypedia_title ) expect fun ResourceStringDesc.getText(): String actual fun ResourceStringDesc.getText(): String = this.toString(appContext )
38. Resources Common val stringDesc = StringDesc.Resource(SharedRes.strings.airlypedia_title ) expect fun ResourceStringDesc.getText(): String actual fun ResourceStringDesc.getText(): String = this.toString(appContext ) actual fun ResourceStringDesc.getText(): String = this.localized()
39. How to read KMM in platforms?
41. dependencies { implementation(project(":shared") ) }
42. dependencies { implementation(project(":shared") ) }
43. dependencies { implementation(project(":shared") ) } New Run Script Phase
44. dependencies { implementation(project(":shared") ) } New Run Script Phase https://kotlinlang.org/docs
45. Next steps • Use async/await in iOS for suspend functions • Try crashlytics, analytics, etc • Use KMM for web app • Share more assets
46. iOS & Android everyday
47. iOS & Android using KMM
48. Is it ready for production?
49. KMM - Pros and Cons • 100% Native • Android developers know 
 Kotlin and Gradle • Optional • Still in Alpha
50. KMM - Pros and Cons • 100% Native • Android developers know 
 Kotlin and Gradle • Optional • Still in Alpha • UI written separately
51. Meet Kotlin Multiplatform Mobile Thanks for listening! Piotr Prus Mobile Tech Lead @Airly GDG 3City Organizer
52. Meet Kotlin Multiplatform Mobile Questions? Piotr Prus Mobile Tech Lead @Airly GDG 3City Organizer