Exploring a KMM Developer’s Toolkit

BlrKotlin May 2023

1. @BlrKotlin KotlinConf’23 Bengaluru Exploring a KMM Developer’s Toolkit Subhrajyoti Sen Motive
2. Agenda • Shared Resources • Parcelable • Dependency Injection • Shared ViewModel • Coroutines • Flow • Build optimizations
3. Shared Resources icerockdev/moko-resources Can be used to share: • Strings • Color • SVG
4. Shared Resources
5. Shared Resources
6. Shared Resources public actual object MR { public actual object strings : ResourceContainer<StringResource> { public actual val now: StringResource = StringResource(R.string.now) public actual val ago: StringResource = StringResource(R.string.ago) } }
7. Shared Resources Initially no region support for localization: fr-CA, es-US, etc. ‼🚨
8. Shared Resources Initially no region support for localization: fr-CA, es-US, etc. ‼🚨 Support added in v0.21.0
9. Shared Resources
10. Shared Resources
11. Shared Resources task("renameAndroidSharedResource") { outputs.upToDateWhen { false } doLast { copy { from("build/generated/moko/androidMain/res/values-fr") into("build/generated/moko/androidMain/res/values-fr-rCA") } delete("build/generated/moko/androidMain/res/values-fr") } dependsOn("generateMRandroidMain") }
12. Shared Resources task("renameIosSharedResource") { outputs.upToDateWhen { false } doLast { copy { from("build/generated/moko/iosMain/res/fr.lproj") into("build/generated/moko/iosMain/res/fr-CA.lproj") } delete("build/generated/moko/iosMain/res/fr.lproj") } dependsOn("generateMRiosMain") }
13. Shared Resources tasks.preBuild { if (tasks.findByName("generateMRiosMain") != null) { dependsOn("renameIosSharedResource") } if (tasks.findByName("generateMRandroidMain") != null) { dependsOn("renameAndroidSharedResource") } }
14. Shared Resources - Localization fun getMyString(): StringDesc { return StringDesc.Resource(MR.strings.my_string) } // Android val string = getMyString().toString(context = this) // iOS let string = getMyString().localized()
15. Shared Resources - Formatting fun getMyFormatDesc(input: String): StringDesc { return MR.strings.my_string_formatted.format(input) } // Android val string = getMyFormatDesc("hello").toString(context = this) // iOS let string = getMyFormatDesc(input: "hello").localized()
16. Shared Resources - Helper // commonMain expect class SharedResource { fun getLocalisedString(string: StringResource, vararg value: Any): String fun getLocalisedString(string: PluralsResource, quantity: Int): String }
17. Shared Resources - Helper // androidMain actual class SharedResource(val context: Application) { actual fun getLocalisedString(string: StringResource, vararg value: Any): String { return string.format(value.asList()).toString(context) } actual fun getLocalisedString(string: PluralsResource, quantity: Int): String { return string.format(quantity, quantity).toString(context) } }
18. Shared Resources - Helper // iosMain actual class SharedResource { actual fun getLocalisedString(string: StringResource, vararg value: Any): String { return string.format(value.asList()).localized() } actual fun getLocalisedString(string: PluralsResource, quantity: Int): String { return string.format(quantity, quantity).localized() } }
19. Shared Resources - Helper // Android val resources = SharedResources(context) val text = resources.getLocalisedString(MR.string.my_string) // iOS let resources = SharedResources() let string = resources.getLocalisedString(MR.strings().my_string())
20. Parcelable // commonMain expect annotation class Parcelize() expect interface Parcelable // androidMain actual typealias Parcelize = Parcelize actual typealias Parcelable = Parcelable // iosMain actual interface Parcelable actual annotation class Parcelize
21. Dependency Injection - Earlier
22. Dependency Injection - Earlier // commonMain open class ChatMessageChannelViewModelImpl( private val messageChannelManager: MessageChannelManagerInterface ) : SharedViewModel(), ChatMessageChannelViewModel
23. Dependency Injection - Earlier // commonMain open class ChatMessageChannelViewModelImpl( private val messageChannelManager: MessageChannelManagerInterface ) : SharedViewModel(), ChatMessageChannelViewModel // android @HiltViewModel class ChatMessageChannelViewModelWrapper @Inject constructor( private val messageChannelManager: MessageChannelManagerInterface, ) : ChatMessageChannelViewModelImpl( messageChannelManager )
24. Dependency Injection - Now
25. Dependency Injection - Now // commonMain actual annotation class KMMViewModel // androidMain actual typealias KMMViewModel = HiltViewModel
26. Dependency Injection - Now // commonMain actual annotation class KMMViewModel // androidMain actual typealias KMMViewModel = HiltViewModel // commonMain @KMMViewModel class ChatMessageChannelViewModelImpl( private val messageChannelManager: MessageChannelManagerInterface ) : SharedViewModel(), ChatMessageChannelViewModel
27. Shared ViewModel
28. Shared ViewModel class CloseableCoroutineScope(context: CoroutineContext) : CoroutineScope { override val coroutineContext: CoroutineContext = context fun close() { coroutineContext.cancel() } }
29. Shared ViewModel // commonMain expect abstract class SharedViewModel { internal val sharedScope: CloseableCoroutineScope protected open fun onCleared() }
30. Shared ViewModel // androidMain actual abstract class SharedViewModel : ViewModel() { actual val sharedScope = CloseableCoroutineScope(SupervisorJob() + Dispatchers.Main) actual override fun onCleared() { super.onCleared() sharedScope.close() } }
31. Shared ViewModel // iosMain actual abstract class SharedViewModel { actual val sharedScope = CloseableCoroutineScope(SupervisorJob() + Dispatchers.Main) protected actual open fun onCleared() { sharedScope.close() } }
32. Coroutines // Kotlin suspend fun asyncFunc() = coroutineScope { launch { delay(1000L) println("World!") } println("Hello") } // Swift func test() { PlatformKt.asyncFunc(completionHandler: { _ in print("Completed") }) }
33. Current Flow Repository UseCase ViewModel Android iOS
34. Coroutines - Dispatchers.IO
35. Coroutines - Dispatchers.IO // commonMain expect fun ktIoDispatcher(): CoroutineDispatcher
36. Coroutines - Dispatchers.IO // commonMain expect fun ktIoDispatcher(): CoroutineDispatcher // androidMain actual fun ktIoDispatcher(): CoroutineDispatcher { return Dispatchers.IO }
37. Coroutines - Dispatchers.IO // commonMain expect fun ktIoDispatcher(): CoroutineDispatcher // androidMain actual fun ktIoDispatcher(): CoroutineDispatcher { return Dispatchers.IO } // iosMain // coroutines 1.7.0-beta private val iosIoDispatcher = newFixedThreadPoolContext(64, "Dispatchers.IO") actual fun ktIoDispatcher(): CoroutineDispatcher { return iosIoDispatcher }
38. Be careful // creates a new thread pool everytime actual fun ktIoDispatcher(): CoroutineDispatcher { return newFixedThreadPoolContext(64, "Dispatchers.IO") }
39. Observable State
40. Observable State interface ChatViewModel { val uiState: KLiveData<ChatUIState> fun method1() fun asyncMethod2() }
41. Observable State interface ChatViewModel { val uiState: KLiveData<ChatUIState> fun method1() fun asyncMethod2() } KLiveData: https://github.com/florent37/Multiplatform-LiveData
42. Coroutines Flow interface ChaViewModel { val uiState: KSharedFlow<ChatUIState> fun method1() fun asyncMethod2() }
43. KFlow open class KStateFlow<T>( private val initialValue: T? = null ) { protected val _flow = MutableStateFlow(initialValue) val flow: StateFlow<T?> = _flow open val value: T? get() = _flow.value }
44. KFlow class KMutableStateFlow<T>( private val initialValue: T? = null ) : KStateFlow<T>(initialValue) { override var value: T? = super._flow.value get() = super._flow.value set(value) { field = value _flow.value = value } }
45. KFlow open class KStateFlow<T>( private val initialValue: T? = null ) { fun collect(scope: KCoroutineScopeInterface, block: (T?) -> Unit) { scope.launch { flow.filterNotNull() .collect { block.invoke(it) } } } }
46. KFlow - iOS class BaseViewController: UIViewController { let scope = KCoroutineScope() deinit { scope.cancel() } }
47. Flow on iOS kmmViewModel.uiState.collect(scope: scope) {[weak self] uiState in guard let uiState = chatUiState else { return } self?.handleKMMUIState(uiState) }
48. KFlow - iOS https://github.com/rickclephas/KMP-NativeCoroutines
49. KFlow - iOS https://github.com/rickclephas/KMP-NativeCoroutines
50. Build Optimizations
51. Build Optimizations • We won’t want to run iOS tasks when running CI for Android • We won’t want to run Android tasks when running CI for iOS
52. Build Optimizations object EnvParams { val disable_iOS: Boolean get() = System.getProperty("disable_iOS") != null val disable_android: Boolean get() = System.getProperty("disable_android") != null } enum class HostType { MAC_OS, ANDROID }
53. Build Optimizations fun KotlinTarget.getHostType(): HostType? = when (platformType) { KotlinPlatformType.androidJvm -> HostType.ANDROID KotlinPlatformType.native -> when { name.startsWith("ios") -> HostType.MAC_OS name.startsWith("watchos") -> HostType.MAC_OS else -> error("Unsupported native target: $this") } else -> null }
54. Build Optimizations fun KotlinTarget.isCompilationAllowed(): Boolean { if (!EnvParams.disable_iOS && !EnvParams.disable_android) { return true } else if (getHostType() == HostType.ANDROID && EnvParams.disable_android) { return false } return !(getHostType() == HostType.MAC_OS && EnvParams.disable_iOS) }
55. Build Optimizations fun KotlinTarget.disableCompilations() { compilations.configureEach { compileKotlinTask.enabled = false } }
56. Build Optimizations fun disableKapt(project: Project) { project.tasks.withType<KaptGenerateStubs>().configureEach { enabled = false } project.tasks.withType<KaptTask>().configureEach { enabled = false } }
57. Build Optimizations fun KotlinTarget.disableCompilationsIfNeeded(project: Project) { if (!isCompilationAllowed()) { disableCompilations() } if (EnvParams.disable_android) { disableKapt(project) } }
58. Build Optimizations // build.gradle.kts kotlin { targets.configureEach { disableCompilationsIfNeeded(project) } }
59. Build Optimizations // build.gradle.kts kotlin { targets.configureEach { disableCompilationsIfNeeded(project) } } https://github.com/arkivanov/gradle-setup-plugin
60. Thank You @iamsubhrajyoti
61. Share your feedback to help us better understand your KotlinConf’23 Global experience!