Troubled Waters: Bridging platform-native SDKs with Kotlin Multiplatform

Talking to native APIs from Kotlin Multiplatform (mostly) Mobile.

Transcript

1. Troubled Waters: Bridging platform-native SDKs with Kotlin Multiplatform Kevin Galligan
2. Partner at Kotlin GDE
3. Touchlab
5. Common JVM JS Native
6. Common JVM JS Native Firebase/JVM Firebase/JS Firebase/iOS
8. Common JVM JS Native Firebase/JVM Firebase/JS Firebase/iOS
9. Common Android iOS Firebase/JVM Firebase/iOS
10. JNI
11. Basic Topics • Tell Kotlin about the native code • Link native code into Kotlin Xcode Framework • API Design
12. Simple First pass it in
13. Interface Driven • 💰 Don’t need cinterop • 💰 No weird linking • 💰 No extra binary size • 🗑 Not easily testable • 🗑 Impractical for complex situations • 🗑 Bad for libraries
14. interface KotlinAnalytics { fun logEvent(name: String, parameters: Map<String, Any>) }
15. interface KotlinAnalytics { fun logEvent(name: String, parameters: Map<String, Any>) } fun initKoinIos( userDefaults: NSUserDefaults, appInfo: AppInfo, analytics: KotlinAnalytics, doOnStartup: () -> Unit ) ( // Etc )
16. class IosAnalytics: KotlinAnalytics { func logEvent(name: String, parameters: [String : Any]) { Analytics.logEvent(name, parameters: parameters) } }
17. class IosAnalytics: KotlinAnalytics { func logEvent(name: String, parameters: [String : Any]) { Analytics.logEvent(name, parameters: parameters) } } KoinIOSKt.doInitKoinIos( userDefaults: userDefaults, appInfo: iosAppInfo, analytics: IosAnalytics(), doOnStartup: doOnStartup )
18. fun withCallback(callback: (Breed) -> Unit) { }
19. viewModel.withCallback(callback: {[weak self] (breed:Breed) -> Void in self?.callMe(breed: breed) })
20. cinterop kotlin calling c/objc
21. cinterop kotlin calling c/objc
22. Call C/Obj-C some swift, some C++
23. *.h cinterop Kotlin/iOS
24. *.h cinterop Kotlin/iOS Binary ? ? ? ? ? ? ? ? ?? ? ?
25. package = co.touchlab.whatever language = Objective-C headers = whatever.h whatever.def
26. other config
27. package = co.touchlab.whatever language = Objective-C headers = whatever.h whatever.def
28. extraOpts = listOf("-mode", "sourcecode")
29. *.h cinterop Kotlin/iOS Binary ? ? ? ? ? ? ? ? ?? ? ?
30. Where are these *.h files? multiple options
31. In Your Repo copy/paste
33. Script Downloads grab headers
34. Truncated Headers feels like cheating a bit :)
36. Cocoapods Dependency the hammer approach
37. kotlin { //etc cocoapods { summary = "Common library for the KaMP starter kit" homepage = "https://github.com/touchlab/KaMPKit" ios.deploymentTarget = "12.4" podfile = project.file("../ios/Podfile") pod("FirebaseAnalytics") } }
38. Docs on Cocoapods/Kotlin https://kotlinlang.org/docs/native-cocoapods-libraries.html
39. cocoapods.FirebaseAnalytics .FIRAnalytics.logEventWithName("someevent", mapOf(/*data*/))
40. Makes project weird can’t run tests, dependency in podspec
41. Carthage ❤ Kotlin https://github.com/wireapp/carthage-gradle-plugin
42. SPM? not yet
43. Linking where is the binary?
44. *.h cinterop Kotlin/iOS Binary ? ? ? ? ? ? ? ? ?? ? ?
45. complex-ish
48. Linking Basics Binary Framework
49. Static Linking Binary Static Framework
50. Dynamic Linking Binary Dynamic Framework
51. Assemble Static Static Framework *.h cinterop Kotlin/iOS Binary ? ? ? ? ? ? ? ??? ? ?
52. Assemble Dynamic *.h cinterop Kotlin/iOS Binary ? ? ? ? ? ? ? ??? ? ? Dynamic Framework
53. Libraries == More Complex recency bias
54. Kermit Crashlytics Firebase.h Firebase
55. Kermit Crashlytics Firebase.h Firebase Dynamic
56. Undefined symbols for architecture x86_64: "_OBJC_CLASS_$_FIRStackFrame", referenced from: objc-class-ref in libco.touchlab:kermit-crashlytics-cache.a(result.o) "_OBJC_CLASS_$_FIRExceptionModel", referenced from: objc-class-ref in libco.touchlab:kermit-crashlytics-cache.a(result.o) "_OBJC_CLASS_$_FIRCrashlytics", referenced from: objc-class-ref in libco.touchlab:kermit-crashlytics-cache.a(result.o) ld: symbol(s) not found for architecture x86_64
57. Undefined symbols for architecture x86_64: "_OBJC_CLASS_$_FIRStackFrame", referenced from: objc-class-ref in libco.touchlab:kermit-crashlytics-cache.a(result.o) "_OBJC_CLASS_$_FIRExceptionModel", referenced from: objc-class-ref in libco.touchlab:kermit-crashlytics-cache.a(result.o) "_OBJC_CLASS_$_FIRCrashlytics", referenced from: objc-class-ref in libco.touchlab:kermit-crashlytics-cache.a(result.o) ld: symbol(s) not found for architecture x86_64
58. stay one lesson ahead…
59. Kotlin/iOS Cocoapods *.h Binary
60. Kotlin/iOS Some Code *.h *.c/*.m
61. Kotlin/iOS *.h *.c/*.m cinterop clang
62. Kotlin/iOS *.h *.c/*.m cinterop
63. Kotlin/iOS *.h *.c/*.m cinterop cklib
64. cklib Links • https://github.com/touchlab/cklib • https://github.com/cashapp/zipline/blob/trunk/ zipline/build.gradle.kts#L157 • https://github.com/touchlab/Kermit/blob/main/ kermit-crashlytics-test/build.gradle.kts#L69
65. Linking Links • https://bpoplauschi.github.io/2021/10/24/Intro-to-static-and-dynamic- libraries-frameworks.html • https://bpoplauschi.github.io/2021/10/25/Advanced-static-vs-dynamic- libraries-and-frameworks.html
66. Testing Binary Framework
67. Kotlin/iOS test.kexe
68. Kotlin/iOS test.kexe Cocoapods *.h Binary Some Code *.h *.c/*.m
69. Kotlin/iOS test.kexe *.h Binary Firebase.h Firebase
70. Kotlin/iOS test.kexe *.h Binary Firebase.h Firebase Stub Binary
72. Kotlin/iOS test.kexe *.h Binary Firebase.h Firebase Stub Binary
73. stay one lesson ahead…
74. API Design thoughts on the common language
75. Uncanny Valley they do the same thing, but…
76. Common Android iOS Firebase/JVM Firebase/iOS
77. Common Android iOS Firebase/JVM Firebase/iOS
78. Common Android iOS C code
79. Common Android iOS C code JNI cinterop bridge
80. Common Android iOS C code JNI cinterop bridge
81. Rules are difficult “it depends” is everything
82. Don’t default expect/actual can be good, can be frustrating
83. expect/actual is less flexible harder to test, etc
84. expect class KotlinAnalytics() { fun logEvent(name: String, parameters: Map<String, Any>) }
85. interface KotlinAnalytics { fun logEvent(name: String, parameters: Map<String, Any>) } expect fun platformAnalyticsFactory(): KotlinAnalytics
87. expect fun platformLogWriter(): LogWriter
88. expect class CrashlyticsLogWriter( minSeverity: Severity = Severity.Info, minCrashSeverity: Severity = Severity.Warn, printTag: Boolean = true ) : LogWriter
89. expect fun crashlyticsLogWriter( minSeverity: Severity = Severity.Info, minCrashSeverity: Severity = Severity.Warn, printTag: Boolean = true ) : LogWriter
90. Service Objects/Small Graph interface and delegates work well
91. Parent<->Child/Larger Graph interface-with-delegates starts looking ugly
92. Order Big Graph/Data Objects getProducts() Product Product Product Supplier
93. Order Big Graph/Data Objects getProducts() Product Product Product Supplier
94. actual typealias with great power…
95. /** * 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 }
96. JVM Side?
97. import java.util.concurrent.atomic.AtomicInteger actual typealias AtomicInt = AtomicInteger
98. Actual needs to match because obviously it does
99. 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) }
100. 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) }
101. Platform Affinity android iOS ?
102. Platform Affinity android iOS android-y
103. typealias can be brittle
104. typealias can be brittle
105. Platform Affinity android iOS android-y JS
106. Parallel Delegates android iOS android-y
107. Empty Typealias everything is extensions
108. 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
109. 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
110. 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
111. 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
112. 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
113. expect open class DocumentSnapshot DocumentSnapshot actual typealias DocumentSnapshot = FIRDocumentSnapshot iOS common actual typealias DocumentSnapshot = com.google.firebase.firestore.DocumentSnapshot Android
114. 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
115. Platform Affinity
116. Platform Agnostic
117. Order Big Graph/Data Objects getProducts() Product Product Product Supplier
118. Order Big Graph/Data Objects getProducts() Product Product Product Supplier
119. Again, that’s rare mostly just use interfaces and delegates!
120. Empty Typealias • https://vimeo.com/371460823 • https://github.com/touchlab-lab/FirestoreKMP
122. API *almost* designs itself you’re mapping existing APIs
123. Iterative Design tweak for platform specifics
124. Platform-Specific Init then common
125. Whatever/ Common Whatever/ Android Whatever/ iOS Whatever AAR Whatever.h Init Init
126. Whatever/ Common Whatever/ Android Whatever/ iOS Whatever AAR Whatever.h Init Init Other Calls
127. Simple First pass it in
128. That was a lot! it’s not all that bad
129. At Touchlab • Big team build tools • Better iOS Dev ex • Swift code generation • Other things
130. If you’re facing these issues… @kpgalligan Kotlin Slack
131. Thanks! @kpgalligan
132. Thanks! @kpgalligan Join the team !