Adit Lal | 2024 Journey of ups/downs for the real-world KMP apps KMP in Practice: Real world case studies

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Coroutines Null-Safety Extension-Functions Smart-Casts Delegated-Properties Versatility on the Server Side streamlined approach Open Source Modern Language Features Uni fi ed Codebase

Kotlin multipla tf Source - https://shorturl.at/xyAPX

Kotlin multipla tf orm

Kotlin multipla tf orm

Kotlin multipla tf orm

Kotlin multipla tf orm

Kotlin multipla tf orm

Kotlin multipla tf orm

Multiplatform libraries

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Compose Multiplatform

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Fleet

• Flexibility to choose what is shared and what not • Shared code lowers the effort, cost per feature • Shared code ensures consistency amongst platforms KMP - Buy in

UseCases - Greenfield #1 a ndroidApp (module) iosApp (module) sh a red (KMP module) a ndroidM a in(source) commonM a in(source) iOSM a in(source) …(source)

UseCases - Greenfield #2 a ndroidApp (module) iosApp (module) a n a lytics (sh a red) Network (sh a red)

UseCases - Brownfield #1 Android Project Regul a r Android code sh a red (KMP module) a ndroidM a in(source) commonM a in(source) iOSM a in(source) iOS Project Regul a r iOS code Dependencies m a n a gement • Coco a Pods • Swift P a ck a ge M a n a ger • M a nu a l fr a mework

UseCases - Brownfield #2 Android Project Regul a r Android code sh a red (KMP module) a ndroidM a in commonM a in iOSM a in iOS Project Regul a r iOS code Dependencies m a n a gement • Coco a Pods • Swift P a ck a ge M a n a ger • M a nu a l fr a mework a n a lytics (sh a red) Network (sh a red)

Adding Multiplatform Mobile to Your Projects • Start small • Keep your shared API simple • Think like a library developer • Implementation should not impact API • Minimise accessibility of everything • Coexist peacefully with (both) platforms

Architecture No Silver Bullets

Architecture No Silver Bullets Multi-layer Architecture

Multi-layer Architecture P r esentation Domain Data

Multi-layer Architecture P r esentation • Sharing is possible to a degree • Prefer MVVM and MVI • Decompose, moko-mvvm • Needs experienced team to share

Multi-layer Architecture • Perfectly shareable • Services, Models, Gateways Domain

Multi-layer Architecture • Usually shareable • Repositories, DTOs and entities • SQLDelight, Realm, Ktor Client, Apollo, kotlinx-datetime Data

Multiplatform UI

Dependency Injection

Ideas, mistakes and learnings

Ideas, mistakes and learnings expect fun debugLog(tag: St r ing, message: St r ing) Expect/Actual

Ideas, mistakes and learnings expect fun debugLog(tag: St r ing, message: St r ing) Expect/Actual impo r t and r oid.util.Log actual fun debugLog(tag: St r ing, message: St r ing) { Log.d(tag, message) } impo r t platfo r m.Foundation.NSLog actual fun debugLog(tag: St r ing, message: St r ing) { if (Platfo r m.isDebugBina r y) { NSLog("%s: %s", tag, message) } }

Ideas, mistakes and learnings inte r nal inte r face XmlFetche r { suspend fun fetchXml(u r l: St r ing) : Pa r se r Input } Interfaces inte r nal class JvmXmlFetche r ( p r ivate val callFacto r y: Call.Facto r y, ) : XmlFetche r { ove r r ide suspend fun fetchXml(u r l: St r ing) : Pa r se r Input { val r equest = c r eateRequest(u r l) r etu r n Pa r se r Input(inputSt r eam = callFacto r y.newCall( r equest).await()) } }

Ideas, mistakes and learnings inte r nal inte r face XmlFetche r { suspend fun fetchXml(u r l: St r ing) : Pa r se r Input } Interfaces inte r nal class IosXmlFetche r ( p r ivate val nsU r lSession: NSURLSession, ) : XmlFetche r { ove r r ide suspend fun fetchXml(u r l: St r ing) : Pa r se r Input = suspendCancellableCo r outine { continuation - > . . . } }

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Gotcha’s •No namespaces •No default parameters •Enums are not Swift-friendly (no values) •Sealed classes are simple classes •Coroutines without cancellation •Flows

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Make it a team effort

Create a library

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How to publish: Android

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How to publish: iOS

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Where to start

You have a blank canvas

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@marcoGomier • Boring code to write multiple times • Code/feature that centralizes the source of truth • Code/feature that can be gradually extracted Where to start?

Kotlin multipla tf orm - 🛠 Tooling 📦 Storage 🏗 Architecture 🔑 Crypto 🗃 Serializer - code and tools - 🍎 Compose UI 🧮 Arithmetic - 📋 Log 📱 Device 🔍 Analytics 📁 File ⏰ Date-Time - 🎨 Graphics 🛢 Resources - 🌎 Network 💉 Dependency Injection 🩺 Test 🚀 Language extensions ➿ Asynchronous 🧩 Service SDK 🔧 Utils

Kotlin multipla tf orm - 2x faster to develop your features business logic - 2x faster writing unit tests - One tech stack - consistency achieved across pla tf orms conclusions

Kotlin multipla tf orm - sta rt small, don’t try to reach 100% of shared logic - be extremely careful with all updates - IDEA, JDK, kotlin, libraries - everything. - keep versioning in mind Suggestions

Kotlin multipla tf orm Kotlin Slack Kotlin O ffi cial Kotlin Training Kotlin by: - h tt ps://jakewha rt on.com/presentations/ - h tt p://antonioleiva.com/kotlin Resources Pay attention to this

Kotlin multipla tf orm h tt ps://github.com/joreilly/PeopleInSpace h tt ps://github.com/joreilly/ClimateTraceKMP h tt ps://github.com/halcyonmobile/Multipla tf ormPlayground About Kotlin Multipla tf orm project with Swi ft UI, Jetpack Compose, Wear Compose, Compose for Desktop, Compose for Web and Kotlin/JS + React clients along with Ktor backend. Resources

• https : //kotlinlang . org/docs/multiplatform . html • https : //kotlinlang . org/docs/native-overview . html • https : //kotlinlang . org/docs/js-overview . html • https : //kotlinlang . org/docs/multiplatform-share-on-platforms . html • https : //kotlinlang . org/docs/multiplatform-connect-to-apis . html • https : //devstreaming-cdn . apple . com/videos/wwdc/2019/416h8485aty341c2/416/416_binary_frameworks_in_swift . pdf • https : //developer . apple . com/videos/play/wwdc2019/416/ • https : //medium . com/@aoriani/list/writing-swiftfriendly-kotlin-multiplatform-apis-c51c2b317fce • https : //kotlinlang . org/docs/native-objc-interop . html • https : //speakerdeck . com/kpgalligan/kotlinconf-2023-kotlin-mobile-multiplatform-for-teams • https : //speakerdeck . com/kpgalligan/sdk-design-and-publishing-for-kotlin-multiplatform-mobile • https : //kotlinlang . org/docs/reference/native/cocoapods . html • https : //kotlinlang . org/docs/multiplatform-build-native-binaries . html#build-xcframeworks • https : //github . com/touchlab/KMMBridge • https : //github . com/prof18/kmp-framework-bundler • https : //github . com/luca992/multiplatform-swiftpackage • https : //github . com/touchlab/xcode-kotlin • https : //github . com/terrakok/kmp-awesome • https : //github . com/AAkira/Kotlin-Multiplatform-Libraries • https : //github . com/touchlab/CrashKiOS • https : //www . droidcon . com/2023/07/31/10-myths-about-crossplatform-mobile-development-with-kotlin/ • https : //blog . jetbrains . com/kotlin/2023/11/kotlin-multiplatform-stable/

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