Experiments with Kotlin Multiplatform

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1. Experiments with Kotlin Multiplatform AndroidHeads Vienna 2019/04/04
2. What is Kotlin Multiplatform?
3. JVM Native JavaScript Kotlin everywhere
4. Multiplatform Project Compilation Targets
5. plugins { id 'kotlin-multiplatform' version '1.3.20' } kotlin { android() iosX64() … } Multiplatform Project Native App commonMain androidMain iosMain
6. expect - actual common expect fun logDebug(tag: String, message: String) import android.util.Log actual fun logDebug(tag: String, message: String) { Log.d(tag, message) } actual fun logDebug(tag: String, message: String) { println("${tag} : ${message}") }
7. Goal: Develop App with Kotlin Multiplatform • Load data from Web-API (Github Jobs API) • Display job information in a list • Persist job data for offline availability
8. UI Activities, Fragments, Views UI ViewController Presenter Presenter UseCases UseCases Repository Repository API Persistance API Persistance Utils Utils
9. UI Activities, Fragments, Views UI ViewController Presenter UseCases Repository API Persistance Utils Shared Library
10. Load Data from API
11. Load Data from API Engine ThreadPool with HttpURLConnections Engine Asynchronous NSURLSession internally
12. Load Data from API @Serializable data class JobPositionDto( @SerialName(“id") val id: String, @SerialName("company") val company: String, @SerialName("location") val location: String, @SerialName("title") val title: String, @SerialName("type") val type: String )
13. Persist Data
14. Repository
15. UI Activities, Fragments, Views UI ViewController Presenter UseCases Repository API Persistance Utils Shared Library Create instance of presenter Call getJobList() in Lifecycle method Implement render() of JobListView
16. Presenter - common class JobsListPresenter(private val view: JobsListView) : BasePresenter(view) { private val repository = JobPositionRepositoryImpl(GithubJobsApi()) fun getJobsList() { view.render(UiState.Loading()) launch(IoDispatcher) { repository.getJobsList().fold({ view.render(UiState.Success(it)) }, { view.render(UiState.Error(Throwable("Loading Jobs failed"))) }) } } }
17. common interface JobsListView: BaseView { fun render(uiState: UiState<List<JobPosition>>) } class MainActivity : AppCompatActivity(), JobsListView { … override fun render(uiState: UiState<List<JobPosition>>) { when (uiState) { is UiState.Success -> { displayJobList(uiState.data) } is UiState.Loading -> { displayProgress() } is UiState.Error -> { displayError(uiState.throwable) } } … }
18. common interface JobsListView: BaseView { fun render(uiState: UiState<List<JobPosition>>) } class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, JobsListView { … func render(uiState: UiState) { if(uiState is UiState.Success){ let state = uiState as! UiState.Success displayJobList(jobs: state.data as! [JobPosition]) } if(uiState is UiState.Loading){ displayProgress() } if(uiState is UiState.Error){ let state = uiState as! UiState.Error displayError(error: state.throwable as! KotlinThrowable) } } … }
20. Ready for Production? Sharing pure logic Sharing architecture
21. • Experimental: Expect lots of changes • Very little documentation, blogposts, samples, … • Only Single-Threaded Coroutines in the common code • Not perfect Swift - Kotlin Interoperability • iOS debugging of the shared library not possible • Important libraries for the common module still missing (e.g. Date) Sharing architecture
22. Summary • Kotlin can run everywhere • Multiplatform Projects: More that one compilation target • Mobile Code Sharing: Everything except the UI and some platform specific functionality can be shared • Sample Application “Kotlin MPP Jobs” • Production-ready only for simple use cases
23. Resources • https://github.com/Lukle/Kotlin-mpp-jobs • @lukleDev on Twitter