Kotlin Multiplatform for Android/iOS devs v2

Presented at DevFest Pisa - 01 April 2023

Transcript

1. Kotlin Multiplatform for Android/iOS devs Paolo Rotolo Mobile developer @ Nextome Anna Labellarte Mobile developer @ Nextome
2. What is Kotlin Multiplaform
3. What is Kotlin Multiplatform
4. What is Kotlin Multiplatform
5. What is Kotlin Multiplatform Kotlin/Native • No Virtual Machine • Targets • iOS • Windows, Linux, Mac • Small devices • Interop with C and obj-C Kotlin/JVM • 100 % interop with Java
6. Kotlin Multiplatform Mobile Image taken from: https://dev.to/anioutkajarkova/kotlin-multiplatform-practical-multithreading-part-1-4357 Kotlin/Native Kotlin/JVM BETA
7. Kotlin Multiplatform Mobile (KMM)BETA
8. Kotlin Multiplatform Mobile (KMM)BETA
9. Why we decided to give it a shot
10. Why we decided to give it a shot - team
11. Why we decided to give it a shot - SDK product workflow
12. Roadmap 1. Validate the idea with a small library
13. Roadmap 2. Transform the existing android project Room Retro fi t Resources DI DateTime
14. Roadmap 3. Make it work for iOS
15. Roadmap 4. Go on with multiplatform 5. Share as much code as we can
16. Pros & Cons ✅ Easy to use ✅ Low risks ✅ Easy integration with native code ✅ Shared codebase ✅ Active Community
17. Pros & Cons ❌ Code generated not Swift-friendly ❌ Build time can be slow on Xcode ❌ Few multiplatform libraries
18. Inside a KMM app
19. Tools Android Studio Kotlin Multiplatform Plugin Xcode / AppCode Kotlin Native Plugin
20. Tools Android Studio Kotlin Multiplatform Plugin Xcode / AppCode Kotlin Native Plugin
21. How to start
22. Root project
25. plugins { kotlin("multiplatform") kotlin("native.cocoapods") id("com.android.library") } kotlin { android() ios() }
26. kotlin { android() ios() sourceSets { val commonMain by getting { dependencies { implementation( "io.ktor:ktor-client-core:$ktor_version") } } val androidMain by getting { dependencies { implementation( "androidx.work:work-runtime-ktx:$work_version") } } val iosMain by getting } }
27. val commonMain by getting { dependencies { implementation( "io.ktor:ktor-client-core:$ktor_version") } } val androidMain by getting { dependencies { implementation( "androidx.work:work-runtime-ktx:$work_version") } } val iosMain by getting } } val commonTest by getting val androidTest by getting val iosTest by getting
30. plugins { kotlin("multiplatform") kotlin("native.cocoapods") id("com.android.library") } kotlin { android() ios() cocoapods { pod("SSZipArchive") } sourceSets { val commonMain by getting { dependencies { implementation( "io.ktor:ktor-client-core:$ktor_version" } }
31. How to write multiplatform code
32. How to write multiplatform code
33. package com.nextome.hellokmm class Greeting { private val platform: Platform = getPlatform() fun greet(): String { return "Hello, ${platform.name}!" } }
34. package com.nextome.hellokmm interface Platform { val name: String } expect fun getPlatform(): Platform
35. package com.nextome.hellokmm import android.os.Build.VERSION class AndroidPlatform : Platform { override val name: String = "Android ${VERSION.SDK_INT}" } actual fun getPlatform(): Platform = AndroidPlatform()
36. package com.nextome.hellokmm import platform.UIKit.UIDevice class IOSPlatform: Platform { override val name: String = UIDevice.currentDevice.systemName() + " " + UIDevice.currentDevice.systemVersion } actual fun getPlatform(): Platform = IOSPlatform()
37. Publish multiplatform libraries
38. / / build.gradle.kts (:shared) plugins { kotlin("multiplatform") id(“com.android.library”) }
39. / / build.gradle.kts (:shared) plugins { kotlin("multiplatform") id(“com.android.library”) id("maven-publish") } group = "com.nextome.hellokmm" version = "1.0.0"
40. // build.gradle.kts (:shared) plugins { kotlin("multiplatform") id(“com.android.library”) id("maven-publish") } group = "com.nextome.hellokmm" version = “1.0.0" kotlin { android{ publishLibraryVariants("release", "debug") } // [ ... ] }
41. ./gradlew publishToMavenLocal // build.gradle.kts (:shared) plugins { kotlin("multiplatform") id(“com.android.library”) id("maven-publish") } group = "com.nextome.hellokmm" version = “1.0.0" kotlin { android{ publishLibraryVariants("release", "debug") }
43. sourceSets { val commonMain by getting { dependencies { implementation("com.nextome.hellokmm:hellokmm:1.0.0") } } } Consume libraries
44. Useful libraries for KMM
45. Room Rx*, LiveData Timber Hilt, Koin SqlDelight / Realm Coroutines & Flow Kermit Koin ➡ ➡ ➡ ➡ Retrofit, OkHttp Gson, Moshi ➡ Ktor ➡ kotlinx-serialization
46. JetPack Multiplatform Libraries Compose DataStore Collections preview preview
47. The Dark side of KMM
48. Make it debuggable on iOS
54. Data Types fun insertNewTodo( title: String, priority: Int )
55. Data Types fun insertNewTodo( title: String, priority: Int ) repository.insertNewTodo( title: String, priority: ? Int32 )
56. Data Types fun insertNewTodo( title: String, priority: Int ) repository.insertNewTodo( title: String, priority: ? ) KotlinInt?
57. Coroutines class TodoRepository { suspend fun fetchTodo(): List<Todo> { val todos = getTodoFromServer() saveToDb(todos) return todos } }
58. Coroutines class TodoRepository { suspend fun fetchTodo(): List<Todo> { val todos = getTodoFromServer() saveToDb(todos) return todos } } scope.launch { val todo = TodoRepository().fetchTodo() }
59. Coroutines class TodoRepository { suspend fun fetchTodo(): List<Todo> { val todos = getTodoFromServer() saveToDb(todos) return todos } } TodoRepository().fetchTodo {todos, error in } func loadTodo() async throws { let todo = try await TodoRepository().fetchTodo() }
60. Coroutines class TodoRepository { suspend fun fetchTodo(): List<Todo> { val todos = getTodoFromServer() saveToDb(todos) return todos } } scope.launch { val todo = TodoRepository().fetchTodo() }
61. Coroutines class TodoRepository { suspend fun fetchTodo(): List<Todo> { val todos = getTodoFromServer() saveToDb(todos) return todos } } scope.launch { val todo = TodoRepository().fetchTodo() } scope.cancel()
62. Koru Inspired by https://touchlab.co/kotlin-coroutines-rxswift/
63. Koru Inspired by https://touchlab.co/kotlin-coroutines-rxswift/ plugins { // add ksp and koru compiler plugin id("com.google.devtools.ksp") version "1.6.21-1.0.6" id("com.futuremind.koru").version("0.11.1") } kotlin { sourceSets { val commonMain by getting { dependencies { // add library dependency implementation("com.futuremind:koru:0.11.1") } } val iosMain by creating { ... } } } koru { nativeSourceSetNames = listOf("iosMain") }
64. Coroutines class TodoRepository { suspend fun fetchTodo(): List<Todo> { val todos = getTodoFromServer() saveToDb(todos) return todos } }
65. Coroutines @ToNativeClass(name = "TodoRepositoryIos") class TodoRepository { suspend fun fetchTodo(): List<Todo> { val todos = getTodoFromServer() saveToDb(todos) return todos } }
66. // build/generated/ksp/TodoRepositoryIos.kt public class TodoRepositoryIos( private val wrapped: TodoRepository, private val scopeProvider: ScopeProvider?, ) { public constructor(wrapped: TodoRepository) : this(wrapped,exportedScopeProvider_mainScopeProvider) public fun fetchTodo(): SuspendWrapper<List<Todo> = SuspendWrapper(scopeProvider, false) { wrapped.fetchTodo() } }
67. Coroutines @ToNativeClass(name = "TodoRepositoryIos") class TodoRepository { suspend fun fetchTodo(): List<Todo> { val todos = getTodoFromServer() saveToDb(todos) return todos } }
68. Coroutines @ToNativeClass(name = "TodoRepositoryIos") class TodoRepository { suspend fun fetchTodo(): List<Todo> { val todos = getTodoFromServer() saveToDb(todos) return todos } } let repo = TodoRepositoryIos( wrapped: TodoRepository(), scope: coroutineScope) repo.getTodoWrapped().subscribe( onSuccess: { (array: NSArray?) -> () in }, onThrow: { throwable in })
69. Coroutines @ToNativeClass(name = "TodoRepositoryIos") class TodoRepository { suspend fun fetchTodo(): List<Todo> { val todos = getTodoFromServer() saveToDb(todos) return todos } } let repo = TodoRepositoryIos( wrapped: TodoRepository(), scope: coroutineScope) repo.getTodoWrapped().subscribe( onSuccess: { (array: NSArray?) -> () in }, onThrow: { throwable in }) SuspendWrapper<List<Todo >>
70. @ToNativeClass(name = "TodoRepositoryIos") class TodoRepository { suspend fun fetchTodo(): List<Todo> { val todos = getTodoFromServer() saveToDb(todos) return todos } }
71. @ToNativeClass(name = "TodoRepositoryIos", launchOnScope = MainScopeProvider :: class) class TodoRepository { suspend fun fetchTodo(): List<Todo> { val todos = getTodoFromServer() saveToDb(todos) return todos } } @ExportedScopeProvider class MainScopeProvider : ScopeProvider { override val scope : CoroutineScope = MainScope() }
72. @ToNativeClass(name = "TodoRepositoryIos", launchOnScope = MainScopeProvider :: class) class TodoRepository { suspend fun fetchTodoList(): TodoList { val todos = getTodoFromServer() saveToDb(todos) return TodoList(todos) } } @ExportedScopeProvider class MainScopeProvider : ScopeProvider { override val scope : CoroutineScope = MainScope() } data class TodoList(val list: List<Todo>)
73. @ToNativeClass(name = "TodoRepositoryIos", launchOnScope = MainScopeProvider :: class) class TodoRepository { suspend fun fetchTodoList(): TodoList { val todos = getTodoFromServer() saveToDb(todos) return TodoList(todos) } } Coroutines let repo = TodoRepositoryIos(wrapped: TodoRepository()) repo.fetchTodoList().subscribe(onSuccess: { (list: TodoList?) in }, onThrow: { (throwable: KotlinThrowable) in })
74. @ToNativeClass(name = "TodoRepositoryIos", launchOnScope = MainScopeProvider :: class) class TodoRepository { suspend fun fetchTodoList(): TodoList { val todos = getTodoFromServer() saveToDb(todos) return TodoList(todos) } } Coroutines let repo = TodoRepositoryIos(wrapped: TodoRepository()) let job = repo.fetchTodoList().subscribe(onSuccess: { (list: TodoList?) in }, onThrow: { (throwable: KotlinThrowable) in }) job.cancel(cause: KotlinCancellationException(message: "Stop it!"))
75. Flow class RandomIntGenerator { fun generateEach(interval: Long) = flow { while(true) { delay(interval) emit(Random.nextInt()) } } }
76. Flow class RandomIntGenerator { fun generateEach(interval: Long) = flow { while(true) { delay(interval) emit(Random.nextInt()) } } } lifecycleScope.launch { RandomIntGenerator().generateEach(ONE_SECOND).collect { print(it) } }
77. Flow class RandomIntGenerator { fun generateEach(interval: Long) = flow { while(true) { delay(interval) emit(Random.nextInt()) } } } RandomIntGenerator() .generateEach(interval: Int64(1000)) .collect(collector: Collector()) { error in } class Collector: Kotlinx_coroutines_coreFlowCollector{ func emit(value: Any?, completionHandler: @escaping (Error?) -> Void) { print(value) completionHandler(nil) } }
78. RandomIntGenerator() .generateEach(interval: Int64(1000)) .collect(collector: Collector()) { error in } class Collector: Kotlinx_coroutines_coreFlowCollector{ func emit(value: Any?, completionHandler: @escaping (Error?) -> Void) { print(value) completionHandler(nil) } }
79. RandomIntGenerator() .generateEach(interval: ONE_SECOND) .collect(collector: Collector<KotlinInt>() { value in print(value) }) { (error) in print(error?.localizedDescription) } class Collector<T>: Kotlinx_coroutines_coreFlowCollector { let callback:(T) -> Void init(callback: @escaping (T) -> Void) { self.callback = callback } func emit(value: Any?, completionHandler: @escaping (Error?) -> Void) { callback(value as! T) completionHandler(nil) } }
80. class RandomIntGenerator { fun generateEach(interval: Long) = flow { while(true) { delay(interval) emit(Random.nextInt()) } } }
81. class RandomIntGenerator { fun generateEach(interval: Long) = flow { while(true) { delay(interval) emit(Random.nextInt()) } } } fun <T> Flow<T>.wrap(): CFlow<T> = CFlow(this) class CFlow<T>(private val origin: Flow<T>) : Flow<T> by origin { fun watch(block: (T) -> Unit): Closeable { val job = Job() onEach { block(it) }.launchIn(CoroutineScope(Dispatchers.Main + job)) return object : Closeable { override fun close() { job.cancel() } } } }
82. class RandomIntGenerator { fun generateEach(interval: Long): CFlow<Int> = flow { while(true) { delay(interval) emit(Random.nextInt()) } }.wrap() } fun <T> Flow<T>.wrap(): CFlow<T> = CFlow(this) class CFlow<T>(private val origin: Flow<T>) : Flow<T> by origin { fun watch(block: (T) > val job = Job() onEach { block(it) }.launchIn(CoroutineScope(Dispatchers.Main + job)) return object : Closeable { override fun close() { job.cancel() } } } }
83. class RandomIntGenerator { fun generateEach(interval: Long): CFlow<Int> = flow { while(true) { delay(interval) emit(Random.nextInt()) } }.wrap() } RandomIntGenerator() .generateEach(interval: ONE_SECOND) .watch { (value: KotlinInt?) in print(value) }
84. let disposable = RandomIntGenerator() .generateEach(interval: ONE_SECOND) .watch { (value: KotlinInt?) in print(value) } disposable.close() class RandomIntGenerator { fun generateEach(interval: Long): CFlow<Int> = flow { while(true) { delay(interval) emit(Random.nextInt()) } }.wrap() }
85. Exception Handling UNCHECKED EXCEPTIONS CHECKED EXCEPTIONS
86. Exception Handling
87. Exception Handling
88. Exception Handling
89. Error Handling
90. Exception Handling
91. Error Handling
92. Default parameters
93. Default parameters
94. Default parameters
95. Default parameters
96. KT-38685
97. Sealed Class
98. Sealed Class
99. Sealed Class when (uiState) { is UIState.Data -> TODO() is UIState.Error - > TODO() is UIState.Loading - > TODO() }
100. Sealed Class
101. Sealed Class Enum
103. Sealed Class
104. Context MyLibrary.getInstance( applicationContext)
105. Context let myLib = MyLibrary.getInstance() myLib.doSomething() val myLib = MyLibrary.getInstance( applicationContext) myLib.doSomething()
106. App Startup internal lateinit var applicationContext: Context private set public object MyLibrary class MyLibraryInitializer: Initializer<MyLibrary> { override fun create(context: Context): MyLibrary { applicationContext = context.applicationContext return MyLibrary } override fun dependencies(): List<Class<out Initializer <*>> > { return listOf() } }
107. Context let myLib = MyLibrary.getInstance() myLib.doSomething() val myLib = MyLibrary.getInstance( applicationContext) myLib.doSomething()
108. Context let myLib = MyLibrary.getInstance() myLib.doSomething() val myLib = MyLibrary.getInstance() myLib.doSomething()
109. Improved ObjC-Swift Interoperability 1.8.0
110. @ObjCName
111. @ObjCName userId: String){ ForUser ( fun deleteTodos TODO() }
112. @ObjCName func deleteTodos } ForUser( userId: String){ userId: String){ ForUser ( fun deleteTodos TODO() }
113. @ObjCName func deleteTodos } ( : String){ forUser fun deleteTodos TODO() } userId: String){ ForUser (
114. @ObjCName func deleteTodos } ( fun deleteTodos TODO() } userId: String){ ForUser ( @ObjCName(“deleteTodos”) @ObjCName(“forUser”) : String){ forUser
115. @HiddenFromObjC
116. @ShouldRefineInSwift
117. @ShouldRefineInSwift fun insertNewTodo( title: String, priority: Int ) ?
118. @ShouldRefineInSwift fun insertNewTodo( title: String, priority: Int ) repository.insertNewTodo( title: String, priority: ? ) KotlinInt? @ShouldRefineInSwift ⚠
119. @ShouldRefineInSwift ⚠ __ insertNewTodo(title: , priority: KotlinInt? ) String func insertNewTodo (title: String, priority: Int?){ }
120. @ShouldRefineInSwift __ func insertNewTodo (title: String, priority: Int?){ } insertNewTodo(title: , priority: ) title priority.toKotlinInt()
122. What about the future
124. Questions?
125. Thanks!