Introducing Kotlin Multiplatform in an existing mobile app - Workshop Edition | GDG Venezia

After discovering a new interesting technology or framework, you will probably start asking yourself how to integrate it into an existing project. That's because, the possibility of starting with a blank canvas is rare (not impossible, but rare).

This is also the case for Kotlin Multiplatform, which is getting more and more hype every day. And now, that the technology has become stable, it's the perfect time to start using it!
In this hands-on session, we will start with an existing Android and iOS application that "lives" in separate repositories, we will extract the business logic from the Android app and share it between the two apps with a Kotlin Multiplatform library. We will also cover how to distribute the library to the existing applications.
By the end of this workshop, you'll have a better understanding of what is needed to start using Kotlin Multiplatform in your existing projects.

Transcript

1. 👨💻 Senior Android Developer @ Airalo Google Developer Expert for Kotlin Marco Gomiero @marcoGomier Introducing Kotlin Multiplatform in an existing mobile app workshop edition
2. @marcoGomier bit.ly/kmp-gdg-venezia
3. @marcoGomier Agenda • [Download Android Studio and the Kotlin Multiplatform Plugin] • [Download Xcode] • Quick intro about Kotlin Multiplatform • Start from an Android and iOS native app - that lives in separate repositories • Extract the business logic into a new KMP library • [Manually and locally] Deploy the library • Replace the business logic on Android and iOS with the KMP library • [BONUS] iOS API enhancements • [BONUS] How to deploy in a scalable way
4. @marcoGomier What is Kotlin Multiplatform?
5. @marcoGomier “Classic” Cross Platform Solutions • All-in approach • Everything is shared, UI included • Different platforms have different patterns
6. @marcoGomier Kotlin Multiplatform • Incremental approach • You choose what to share (even UI, if you want)
7. @marcoGomier Photo by Erwan Hesry on Unsplash 💡 Create a library!
8. @marcoGomier Common Kotlin Kotlin/JVM Kotlin/JS Kotlin/Native JVM Android Browser NodeJS iOS macOS watchOS tvOS Linux Windows Supported Platforms Kotlin/Wasm Browser Alpha
9. @marcoGomier Common Kotlin Kotlin/JVM Kotlin/JS Kotlin/Native JVM Android Browser NodeJS iOS macOS watchOS tvOS Linux Windows Mobile Kotlin/Wasm Browser Alpha
10. @marcoGomier How it works?
11. @marcoGomier shared androidApp iosApp Library Library iOS Android
12. @marcoGomier shared androidApp Gradle Module Android Same repository
13. @marcoGomier shared androidApp .aar Android Different repositories
14. @marcoGomier iosApp iOS shared XCFramework Different repositories Same repository
15. @marcoGomier XCFramework https://developer.apple.com/documentation/xcode/creating-a-multi-platform-binary-framework-bundle
16. @marcoGomier NEW https://devstreaming-cdn.apple.com/videos/wwdc/2019/416h8485aty341c2/416/416_binary_frameworks_in_swift.pdf
17. @marcoGomier https://devstreaming-cdn.apple.com/videos/wwdc/2019/416h8485aty341c2/416/416_binary_frameworks_in_swift.pdf NEW iOS mac OS watch OS tvOS
18. @marcoGomier shared androidApp iosApp Gradle Module XCFramework Same Repository Easier for new projects
19. @marcoGomier Common Kotlin Android App iOS App .aar XCFramework Android App Repository KMP Repository iOS App Repository Easier for existing projects
20. @marcoGomier Code Time 🧑💻
21. @marcoGomier bit.ly/kmp-existing-workshop
22. @marcoGomier Code Time 🧑💻
23. @marcoGomier XCFramework https://developer.apple.com/documentation/xcode/creating-a-multi-platform-binary-framework-bundle
24. @marcoGomier iOS Dependency Managers • CocoaPods • Carthage • Swift Package Manager 💀 💀 ✅
25. @marcoGomier Swift Package Manager • Based on git • Configured with a Package.swift file • Semantic versioning (e.g. 1.2.3) with git tags • Can contain code or binaries • Can be local or remote, it’s git!
26. @marcoGomier Code Time 🧑💻
27. @marcoGomier Kotlin -> Obj-c -> Swift
28. @marcoGomier Code Time 🧑💻
29. @marcoGomier Some gotchas • No namespaces • No default parameters • Enums are not Swift-friendly (no values) • Sealed classes are simple classes • Coroutines without cancellation • Flows
30. @marcoGomier Code Time 🧑💻
31. @marcoGomier Swift Package Manager • Manual is boring and not scalable • Use some tooling and public artifactories
32. @marcoGomier Code Time 🧑💻
33. @marcoGomier Conclusions • You choose what to share (even UI, if you want) • Validate the process with “little” effort • Then you can go bigger and share more “features”
34. Bibliography / Useful Links • https: / / developer.apple.com/documentation/xcode/creating-a-multi-platform-binary-framework- bundle • https: / / devstreaming-cdn.apple.com/videos/wwdc/ 2019/416h8485aty341c2/416/416_binary_frameworks_in_swift.pdf • https: / / kotlinlang.org/docs/multiplatform-build-native-binaries.html • https: / / developer.apple.com/documentation/xcode/distributing-binary-frameworks-as-swift- packages • https: / / github.com/rickclephas/KMP-NativeCoroutines • https: / / skie.touchlab.co/ • https: / / github.com/luca992/multiplatform-swiftpackage • https: / / kmmbridge.touchlab.co/ • https: / / medium.com/geekculture/xcode-13-3-supports-spm-binary-dependency-in-private-github- release-8d60a47d5e45 • https: / / touchlab.co/xcodekotlin
35. @marcoGomier Thank you! > Twitter: @marcoGomier > Github: prof18 > Website: marcogomiero.com > Mastodon: androiddev.social/@marcogom 👨💻 Senior Android Developer @ Airalo Google Developer Expert for Kotlin Marco Gomiero bit.ly/kmp-gdg-venezia