Kotlin Multiplatform Libraries

Thoughts on building libraries for KMP.

Transcript

1. Kotlin Multiplatform Libraries Kevin Galligan
2. Touchlab
4. Libraries are crucial
6. -Kevin Galligan “Shared UI is a history of pain and failure. Shared logic is the history of computers.”
7. “The easiest overhead to predict with C++ is the need to build frameworks and libraries” -Eyal Guthmann (Dropbox blog post author)
8. KMP is no exception in fact, more so
9. KMP is lean
10. You don’t get • Concurrency • Locale • Date/Time • File I/O • Networking • (most of JRE)
11. Big hill to climb however…
12. Kotlin ecosystem is strong lot’s of stuff out there
13. decade of android libraries
14. Very engaged community you’re here, right?
15. Why consider KMP?
16. lots of interest
17. lots of interest
18. Growth in deployment much more in 2020
19. Android ecosystem is crowded hard to get focus
20. Great time to get in much bigger impact
21. What is Kotlin Multiplatform?
22. Common JVM JS Native
23. Common JVM JS Native iOS Mac Linux Windows Android/NDK Wasm Others… Java-6 Java-8 Android Browser Node
24. Common JVM JS Native iOS Mac Linux Windows Android/NDK Wasm Others… Java-6 Java-8 Android Browser Node
25. Common JVM JS Native iOS (arm 64) Java-6 Java-8 Android Browser Node
26. Common Native iOS (arm 64) Xcode framework
27. Common Native iOS (arm 64) klib Xcode framework
28. Common JVM Android
29. Common JVM Android App
30. Common JVM Android App AAR
31. Library Patterns
32. Just Code not super complicated
33. SDK Wrapper Firestore SDK
34. Not super clear cut most libraries are a mix
35. Published SDK many from one
36. Platform Specific Logic
37. expect/actual
38. //In common code expect val isMainThread: Boolean
39. //In common code expect val isMainThread: Boolean //In Android/JVM actual val isMainThread: Boolean get() = Looper.getMainLooper() === Looper.myLooper()
40. //In common code expect val isMainThread: Boolean //In Android/JVM actual val isMainThread: Boolean get() = Looper.getMainLooper() === Looper.myLooper() //In iOS/native code actual val isMainThread: Boolean get() = NSThread.isMainThread()
41. //Value expect val isMainThread: Boolean
42. //Value expect val isMainThread: Boolean //Function expect fun myFun():String
43. //Value expect val isMainThread: Boolean //Function expect fun myFun():String //Class expect class MyClass { fun heyo(): String }
44. //Value expect val isMainThread: Boolean //Function expect fun myFun():String //Class expect class MyClass { fun heyo(): String } //Object expect object MyObject { fun heyo(): String }
45. //Value expect val isMainThread: Boolean //Function expect fun myFun():String //Class expect class MyClass { fun heyo(): String } //Object expect object MyObject { fun heyo(): String } //Annotation @Target(AnnotationTarget.FUNCTION, AnnotationTarget.CONSTRUCTOR) @Retention(AnnotationRetention.SOURCE) expect annotation class Throws(vararg val exceptionClasses: KClass<out Throwable>)
46. actual typealias with great power…
47. /** * Multiplatform AtomicInt implementation */ expect class AtomicInt(initialValue: Int) { fun get(): Int fun set(newValue: Int) fun incrementAndGet(): Int fun decrementAndGet(): Int fun addAndGet(delta: Int): Int fun compareAndSet(expected: Int, new: Int): Boolean }
48. JVM Side?
49. import java.util.concurrent.atomic.AtomicInteger actual typealias AtomicInt = AtomicInteger
50. Actual needs to match because obviously it does
51. import kotlin.native.concurrent.AtomicInt actual class AtomicInt actual constructor(initialValue:Int){ private val atom = AtomicInt(initialValue) actual fun get(): Int = atom.value actual fun set(newValue: Int) { atom.value = newValue } actual fun incrementAndGet(): Int = atom.addAndGet(1) actual fun decrementAndGet(): Int = atom.addAndGet(-1) actual fun addAndGet(delta: Int): Int = atom.addAndGet(delta) actual fun compareAndSet(expected: Int, new: Int): Boolean = atom.compareAndSet(expected, new) }
52. import kotlin.native.concurrent.AtomicInt actual class AtomicInt actual constructor(initialValue:Int){ private val atom = AtomicInt(initialValue) actual fun get(): Int = atom.value actual fun set(newValue: Int) { atom.value = newValue } actual fun incrementAndGet(): Int = atom.addAndGet(1) actual fun decrementAndGet(): Int = atom.addAndGet(-1) actual fun addAndGet(delta: Int): Int = atom.addAndGet(delta) actual fun compareAndSet(expected: Int, new: Int): Boolean = atom.compareAndSet(expected, new) }
53. Platform Affinity android iOS ?
54. Platform Affinity android iOS android-y
55. Platform Affinity android iOS iOS-ish
56. Platform Affinity android iOS iOS-ish JS
57. Parallel Delegates android iOS android-y
58. (Maybe) Optimize for JVM (if) most of your users
59. Stately has a fair bit of stuff
60. Minimal JVM-side impact
61. typealias can be brittle
62. Prefer Interfaces for “service” objects
63. public interface Settings { public fun clear() public fun remove(key: String) public fun hasKey(key: String): Boolean public fun putInt(key: String, value: Int) public fun getInt(key: String, defaultValue: Int = 0): Int public fun getIntOrNull(key: String): Int? public fun putLong(key: String, value: Long) public fun getLong(key: String, defaultValue: Long = 0): Long public fun getLongOrNull(key: String): Long? //Etc... } from https://github.com/russhwolf/multiplatform-settings
64. expect fun platformSettings():Settings
65. object ServiceRegistry { var sessionizeApi:SessionizeApi by ThreadLocalDelegate() var analyticsApi: AnalyticsApi by FrozenDelegate() var notificationsApi:NotificationsApi by FrozenDelegate() var dbDriver: SqlDriver by FrozenDelegate() var cd: CoroutineDispatcher by FrozenDelegate() var appSettings: Settings by FrozenDelegate() var concurrent: Concurrent by FrozenDelegate() var timeZone: String by FrozenDelegate() //Etc… from https://github.com/touchlab/DroidconKotlin/
66. Just an Interface no expect/actual required
67. class TestSettings:Settings { private val map = frozenHashMap<String, Any?>() override fun clear() { map.clear() } override fun getBoolean(key: String, defaultValue: Boolean): Bo return if(map.containsKey(key)){ map[key] as Boolean }else{ defaultValue } } //Etc… from https://github.com/touchlab/DroidconKotlin/
68. object ServiceRegistry { var sessionizeApi:SessionizeApi by ThreadLocalDelegate() var analyticsApi: AnalyticsApi by FrozenDelegate() var notificationsApi:NotificationsApi by FrozenDelegate() var dbDriver: SqlDriver by FrozenDelegate() var cd: CoroutineDispatcher by FrozenDelegate() var appSettings: Settings by FrozenDelegate() var concurrent: Concurrent by FrozenDelegate() var timeZone: String by FrozenDelegate() //Etc… from https://github.com/touchlab/DroidconKotlin/
69. Minimize expect/actual Droidcon App: 9 functions, 2 classes
70. https://go.touchlab.co/dcrw
71. Firestore SDK wrapping multiple clients
72. 2 (or more) Similar Things but not the same
73. Platform Affinity android iOS ?
74. Empty Typealias wait, hear me out
76. Platform Affinity
77. Platform Agnostic
78. Empty Typealias everything is extensions
79. expect class QuerySnapshot expect val QuerySnapshot.documentChanges_:List<DocumentChange> expect fun QuerySnapshot.getDocumentChanges_(…):List<DocumentChange> expect val QuerySnapshot.documents_:List<DocumentSnapshot> expect val QuerySnapshot.metadata: SnapshotMetadata expect val QuerySnapshot.query: Query expect val QuerySnapshot.empty: Boolean expect val QuerySnapshot.size: Int
80. expect class QuerySnapshot expect val QuerySnapshot.documentChanges_:List<DocumentChange> expect fun QuerySnapshot.getDocumentChanges_(…):List<DocumentChange> expect val QuerySnapshot.documents_:List<DocumentSnapshot> expect val QuerySnapshot.metadata: SnapshotMetadata expect val QuerySnapshot.query: Query expect val QuerySnapshot.empty: Boolean expect val QuerySnapshot.size: Int
81. actual typealias QuerySnapshot = FIRQuerySnapshot actual val QuerySnapshot.documentChanges_: List<DocumentChange> get() = documentChanges as List<DocumentChange> actual val QuerySnapshot.documents_: List<DocumentSnapshot> get() = documents as List<DocumentSnapshot> actual fun QuerySnapshot.getDocumentChanges_(metadataChanges: Metadata documentChangesWithIncludeMetadataChanges(metadataChanges == Metad iOS
82. actual typealias QuerySnapshot = FIRQuerySnapshot actual val QuerySnapshot.documentChanges_: List<DocumentChange> get() = documentChanges as List<DocumentChange> actual val QuerySnapshot.documents_: List<DocumentSnapshot> get() = documents as List<DocumentSnapshot> actual fun QuerySnapshot.getDocumentChanges_(metadataChanges: Metadata documentChangesWithIncludeMetadataChanges(metadataChanges == Metad iOS
83. actual typealias QuerySnapshot = FIRQuerySnapshot actual val QuerySnapshot.documentChanges_: List<DocumentChange> get() = documentChanges as List<DocumentChange> actual val QuerySnapshot.documents_: List<DocumentSnapshot> get() = documents as List<DocumentSnapshot> actual fun QuerySnapshot.getDocumentChanges_(metadataChanges: Metadata documentChangesWithIncludeMetadataChanges(metadataChanges == Metad iOS
84. expect open class DocumentSnapshot DocumentSnapshot actual typealias DocumentSnapshot = FIRDocumentSnapshot iOS common actual typealias DocumentSnapshot = com.google.firebase.firestore.DocumentSnapshot Android
85. actual typealias QuerySnapshot = com.google.firebase.firestore.QuerySn actual val QuerySnapshot.documentChanges_: List<DocumentChange> get() = documentChanges actual val QuerySnapshot.documents_: List<DocumentSnapshot> get() = documents actual fun QuerySnapshot.getDocumentChanges_(metadataChanges: Metadata getDocumentChanges(metadataChanges.toJvm()) Android
86. Watch Return Types be careful of matching signatures
87. expect fun FirebaseFirestore.disableNetwork_():TaskVoid
88. expect fun FirebaseFirestore.disableNetwork_():TaskVoid actual fun FirebaseFirestore.disableNetwork_(): TaskVoid = TaskVoid(disableNetwork())
89. expect fun FirebaseFirestore.disableNetwork_():TaskVoid actual fun FirebaseFirestore.disableNetwork_(): TaskVoid = TaskVoid(disableNetwork()) public Task<Void> disableNetwork() { this.ensureClientConfigured(); return this.client.disableNetwork(); }
90. Again, Prefer Interfaces for service objects
91. expect fun getFirebaseInstance():FirebaseFirestore expect class FirebaseFirestore expect fun FirebaseFirestore.batch(): WriteBatch expect fun FirebaseFirestore.collection(collectionPath:String):Collect expect fun FirebaseFirestore.collectionGroup(collectionId:String):Quer expect fun FirebaseFirestore.disableNetwork_():TaskVoid expect fun FirebaseFirestore.document(documentPath:String):DocumentRef expect fun FirebaseFirestore.enableNetwork_():TaskVoid expect var FirebaseFirestore.settings:FirebaseFirestoreSettings
92. expect fun getFirebaseInstance():FirebaseFirestore interface FirebaseFirestore{ fun batch(): WriteBatch fun collection(collectionPath:String):CollectionReference fun collectionGroup(collectionId:String):Query fun disableNetwork():TaskVoid fun document(documentPath:String):DocumentReference fun enableNetwork():TaskVoid var FirebaseFirestore.settings:FirebaseFirestoreSettings }
93. Minimize expect/actual? Firestore SDK: 100+ ‘expect’ instances
94. Which to use? • Interfaces when reasonable • Singletons and service objects for sure • Easier to test • typealias when you need a bunch of things and don’t want a parallel delegate hierarchy • Data classes and type hierarchies get complicated with interfaces
95. Inline Classes the other option
96. inline class Name(val s: String) { val length: Int get() = s.length fun greet() { println("Hello, $s") } }
97. inline class Name(val s: String) { val length: Int get() = s.length fun greet() { println("Hello, $s") } }
98. Experimental had some trouble, but promising (1.3.70?)
99. Function args! swift friendly
100. fun initLambdas( staticFileLoader: (filePrefix: String, fileType: String) -> String?, clLogCallback: (s: String) -> Unit, softExceptionCallback: (e:Throwable, message:String) - >Unit)
101. func loadAsset(filePrefix:String, fileType:String) -> String?{ do{ let bundleFile = Bundle.main.path(forResource: filePrefix, ofType: fileType) return try String(contentsOfFile: bundleFile!) } catch { return nil } }
102. Hard(er) to test interfaces and functions are stubs
103. Objc Platform Interop? sure, but meh
104. configure([targets.iosX64, targets.iosArm64 ]) { compilations.main.source(sourceSets.iosMain) compilations.test.source(sourceSets.iosTest) compilations["main"].cinterops { firebasecore { packageName 'cocoapods.FirebaseCore' defFile = file("$projectDir/src/iosMain/c_interop/FirebaseCore.def") includeDirs ("$projectDir/../iosApp/Pods/FirebaseCore/Firebase/Core/Public") compilerOpts ("-F$projectDir/src/iosMain/c_interop/modules/FirebaseCore-$ {versions.firebaseCoreIos}") } firestore { packageName 'cocoapods.FirebaseFirestore' defFile = file("$projectDir/src/iosMain/c_interop/FirebaseFirestore.def") includeDirs ("$projectDir/../iosApp/Pods/FirebaseFirestore/Firestore/Source/Public", "$projectDir/../iosApp/Pods/FirebaseCore/Firebase/Core/Public") compilerOpts ("-F$projectDir/src/iosMain/c_interop/modules/FirebaseFirestore-$ {versions.firebaseFirestoreIos}") } } }
105. configure([targets.iosX64, targets.iosArm64 ]) { compilations.main.source(sourceSets.iosMain) compilations.test.source(sourceSets.iosTest) compilations["main"].cinterops { firebasecore { packageName 'cocoapods.FirebaseCore' defFile = file("$projectDir/src/iosMain/c_interop/FirebaseCore.def") includeDirs ("$projectDir/../iosApp/Pods/FirebaseCore/Firebase/Core/Public") compilerOpts ("-F$projectDir/src/iosMain/c_interop/modules/FirebaseCore-$ {versions.firebaseCoreIos}") } firestore { packageName 'cocoapods.FirebaseFirestore' defFile = file("$projectDir/src/iosMain/c_interop/FirebaseFirestore.def") includeDirs ("$projectDir/../iosApp/Pods/FirebaseFirestore/Firestore/Source/Public", "$projectDir/../iosApp/Pods/FirebaseCore/Firebase/Core/Public") compilerOpts ("-F$projectDir/src/iosMain/c_interop/modules/FirebaseFirestore-$ {versions.firebaseFirestoreIos}") } } }
106. configure([targets.iosX64, targets.iosArm64 ]) { compilations.main.source(sourceSets.iosMain) compilations.test.source(sourceSets.iosTest) compilations["main"].cinterops { firebasecore { packageName 'cocoapods.FirebaseCore' defFile = file("$projectDir/src/iosMain/c_interop/FirebaseCore.def") includeDirs ("$projectDir/../iosApp/Pods/FirebaseCore/Firebase/Core/Public") compilerOpts ("-F$projectDir/src/iosMain/c_interop/modules/FirebaseCore-$ {versions.firebaseCoreIos}") } firestore { packageName 'cocoapods.FirebaseFirestore' defFile = file("$projectDir/src/iosMain/c_interop/FirebaseFirestore.def") includeDirs ("$projectDir/../iosApp/Pods/FirebaseFirestore/Firestore/Source/Public", "$projectDir/../iosApp/Pods/FirebaseCore/Firebase/Core/Public") compilerOpts ("-F$projectDir/src/iosMain/c_interop/modules/FirebaseFirestore-$ {versions.firebaseFirestoreIos}") } } }
107. @ExternalObjCClass open class FIRAppMeta : NSObjectMeta { val allApps: Map<Any?, *>? @ObjCMethod("allApps", "@16@0:8") external get @ObjCMethod("configure", "v16@0:8") external open fun configure(): Unit @ObjCMethod("configureWithOptions:", "v24@0:8@16") external open fun configureWithOptions(options: FIROptions): Unit @ObjCMethod("configureWithName:options:", "v32@0:8@16@24") external open fun configureWithName(name: String, options: FIROptions): Unit @ObjCMethod("defaultApp", "@16@0:8") external open fun defaultApp(): FIRApp? @ObjCMethod("appNamed:", "@24@0:8@16") external open fun appNamed(name: String): FIRApp? @ObjCMethod("allApps", "@16@0:8")
108. Interop can be tricky with library brittle config (imho)
109. Or…
110. interface AnalyticsApi { fun logEvent(name: String, params: Map<String, Any>) }
111. class FirebaseAnalyticsApi: AnalyticsApi{ func logEvent(name: String, params: [String : Any]) { Analytics.logEvent(name, parameters: params) } }
112. Firestore SDK needs objc maybe your library doesn’t
113. Firestore SDK https://github.com/touchlab/FirestoreKMP
114. Soft Launch: Crash Reporting
115. Symbolicated Kotlin Crashes Crashlytics & Bugsnag
116. The Problem different platforms
117. Kotlin has Exceptions iOS mostly just crashes
118. konan::abort()
119. Throwable stack
120. iOS Needs Interop Crashlytics & Bugsnag libraries
121. class CrashNSException: NSException { init(callStack:[NSNumber], exceptionType: String, message: String) { super.init(name: NSExceptionName(rawValue: exceptionType), reason: message, userInfo: nil) self._callStackReturnAddresses = callStack } required init?(coder: NSCoder) { fatalError("init(coder:) has not been implemented") } private lazy var _callStackReturnAddresses: [NSNumber] = [] override var callStackReturnAddresses: [NSNumber] { get { return _callStackReturnAddresses } set { _callStackReturnAddresses = newValue } } } class BugsnagCrashHandler: CrashkiosCrashHandler { override func crashParts(addresses: [KotlinLong], exceptionType: String, message: String) { Bugsnag.notify(CrashNSException(callStack: addresses, exceptionType: exceptionType, message: message)) } }
122. class CrashlyticsCrashHandler: CrashkiosCrashHandler { override func crashParts( addresses: [KotlinLong], exceptionType: String, message: String) { let clsStackTrace = addresses.map { CLSStackFrame(address: UInt(truncating: $0)) } Crashlytics.sharedInstance().recordCustomExceptionName( exceptionType, reason: message, frameArray: clsStackTrace ) } }
123. CrashKiOS https://github.com/touchlab/CrashKiOS
124. CrashKiOS https://github.com/touchlab/CrashKiOS
125. Publishing/CI
126. Publishing • Maven Central • Bintray (jcenter) • Jitpack does not work
127. Maven Central • https://central.sonatype.org/pages/ossrh-guide.html • https://github.com/cashapp/sqldelight • https://github.com/touchlab/FirestoreKMP
128. Bintray natanfudge.github.io/fudgedocs/publish-kotlin-mpp-lib.html
129. CI • Travis by a lot of the Square stuff • We’ve had some luck with “App Center” • Moving to Azure Pipelines as it makes Windows easier
130. Getting Started go.touchlab.co/kmplib
131. take a break!
132. General Thoughts
133. Big Blockers stuff we’re waiting on
134. Compiler Plugins no kapt
135. Multithreaded Coroutines cascading issue
138. What does that mean?
139. go.touchlab.co/dcktsrc
141. Institutional Libraries the usual stuff
142. Institutional Libraries •Date/Time •Locale •Files •I/O
143. date libraries
144. date libraries
145. date libraries
146. date libraries
147. date libraries
148. What to work on? be a little careful
149. Skip date/time libraries that’s covered
150. Mocking no reflection or compiler plugins
151. Mockk wants help
152. What about Swift? no reflection, no surrender
153. interface HeyStuff { fun myFun(): String val myVal: Int }
154. interface HeyStuff { fun myFun(): String val myVal: Int } class MockStuff:HeyStuff{ }
155. interface HeyStuff { fun myFun(): String val myVal: Int } class MockStuff:HeyStuff{ }
156. File I/O probably OK
157. Server Contract swagger, graphql, grpc
158. Architecture big word
159. Reactive Border LiveData analog? RxSwift?
160. Logging waiting on timber
161. UI? wait, I thought…
162. Join the Slack let’s work together
163. Avoid Library Bikeshedding!
164. Touchlab Stuff
165. Some Stuff • Kotlin Xcode Plugin • Xcode Sync (get you Kotlin in Xcode) • Stately • Sqliter (Sqlite Driver under Sqldelight on native)
166. KMP evaluation kit
167. KaMP-Kit go.touchlab.co/KaMP-Kit
168. Thanks! @kpgalligan touchlab.co
169. Thanks! @kpgalligan touchlab.co Join the team !