Kotlin Budapest Meetup I 2024 Tamas Fabian Principal Android Software Engineer October 17, 2024 Mastering Dependencies in Kotlin Multiplatform 

Kotlin Budapest Meetup I 2024 Agenda 1. Story time 2. Basics 3. Dependencies in Kotlin Multiplatform 4. Platform-specific deps 5. Common issues 

Kotlin Budapest Meetup I 2024 Story time 

Kotlin Budapest Meetup I 2024 The Project The company's chat application is in need of an overhaul. Two principal Native Mobile Developers got hired. Options: - Refactor - Reimplement native apps - Or... guess what? 

Kotlin Budapest Meetup I 2024 

Kotlin Budapest Meetup I 2024 Basics 

Kotlin Budapest Meetup I 2024 Basics commonMain nativeMain androidNativeMain appleMain iosMain iosArm64Main iosSimulatorArm64M ain macosMain tvosMain watchosMain linuxMain mingwMain androidMain jvmMain compilation main .classfiles jsMain compilation test .classfiles commonTest jvmTest compilation main .js jsTest compilation test .js nativeTest androidNativeTest appleTest iosTest iosArm64Test iosSimulatorArm64T est macosTest tvosTest watchosTest linuxTest mingwTest androidTest jvm target js target 

Kotlin Budapest Meetup I 2024 Part of the build responsible for compiling, testing, and packaging a piece of software targeting one of the supported platforms. • Presets for supported platforms Targets Basics kotlin { applyDefaultHierarchyTemplate() androidTarget() iosX64(), iosArm64(), iosSimulatorArm64() } 

Kotlin Budapest Meetup I 2024 Part of the build responsible for compiling, testing, and packaging a piece of software targeting one of the supported platforms. • Presets for supported platforms Targets Basics kotlin { applyDefaultHierarchyTemplate() androidTarget() iosX64(), iosArm64(), iosSimulatorArm64() } 

Kotlin Budapest Meetup I 2024 Part of the build responsible for compiling, testing, and packaging a piece of software targeting one of the supported platforms. • Presets for supported platforms Targets Basics kotlin { applyDefaultHierarchyTemplate { common { group("posix") { withLinux() withMingw() withMacos() } } } 

Kotlin Budapest Meetup I 2024 Part of the build responsible for compiling, testing, and packaging a piece of software targeting one of the supported platforms. • Presets for supported platforms • Common & Target-specific configurations Targets Basics kotlin { androidTarget { @OptIn(ExperimentalKotlinGradlePluginApi::class) compilerOptions { jvmTarget.set(JvmTarget.JVM_11) } } } 

Kotlin Budapest Meetup I 2024 Part of the build responsible for compiling, testing, and packaging a piece of software targeting one of the supported platforms. • Presets for supported platforms • Common & Target-specific configurations Targets Basics kotlin { listOf( iosX64(), iosArm64(), iosSimulatorArm64() ).forEach { iosTarget -> iosTarget.binaries.framework { baseName = "Shared" isStatic = true } } } 

Kotlin Budapest Meetup I 2024 Part of the build responsible for compiling, testing, and packaging a piece of software targeting one of the supported platforms. • Presets for supported platforms • Common & Target-specific configurations • One or more compilations Targets Basics 

Kotlin Budapest Meetup I 2024 Compilations are used for defining the way how final artifacts are produced. • JVM, JS, Native: main & test Compilations Basics kotlin { jvm { val main by compilations.getting { compilerOptions.configure { jvmTarget.set(JvmTarget.JVM_17) } } } } 

Kotlin Budapest Meetup I 2024 Compilations are used for defining the way how final artifacts are produced. • JVM, JS, Native: main & test • Android: by build variants Compilations Basics kotlin { jvm { val main by compilations.getting { compilerOptions.configure { jvmTarget.set(JvmTarget.JVM_17) } } } } 

Kotlin Budapest Meetup I 2024 A source set is a set of source files with its own targets, dependencies, and compiler options. It's the main way to share code in multiplatform projects. • Unique name • Predefined source sets • commonMain • SourceSets Basics sourceSets { commonMain.dependencies { //put your multiplatform dependencies here } commonTest.dependencies { implementation(libs.kotlin.test) } } 

Kotlin Budapest Meetup I 2024 A source set is a set of source files with its own targets, dependencies, and compiler options. It's the main way to share code in multiplatform projects. • Unique name • Predefined source sets • commonMain • SourceSets Basics sourceSets { commonMain.dependencies { implementation(libs.kotlinx.coroutines.core) } jsMain.dependencies { implementation(libs.kotlinx.coroutines.core-js) } } 

Kotlin Budapest Meetup I 2024 A source set is a set of source files with its own targets, dependencies, and compiler options. It's the main way to share code in multiplatform projects. • Unique name • Predefined source sets • commonMain • • Intermediate source sets SourceSets Basics sourceSets { val commonJvm by creating { dependsOn(commonMain.get()) dependencies { implementation(libs.socketIo) } } androidMain { dependsOn(commonJvm) } jvmMain { dependsOn(commonJvm) } } 

Kotlin Budapest Meetup I 2024 A source set is a set of source files with its own targets, dependencies, and compiler options. It's the main way to share code in multiplatform projects. • Unique name • Predefined source sets • commonMain • • Intermediate source sets • DSL reference SourceSets Basics 

Kotlin Budapest Meetup I 2024 Basics commonMain nativeMain androidNativeMain appleMain iosMain iosArm64Main iosSimulatorArm64M ain macosMain tvosMain watchosMain linuxMain mingwMain androidMain jvmMain compilation main .classfiles jsMain compilation test .classfiles commonTest jvmTest compilation main .js jsTest compilation test .js nativeTest androidNativeTest appleTest iosTest iosArm64Test iosSimulatorArm64T est macosTest tvosTest watchosTest linuxTest mingwTest androidTest jvm target js target 

Kotlin Budapest Meetup I 2024 Dependencies in Kotlin Multiplatform 

Kotlin Budapest Meetup I 2024 You can set them at: • Source set level api, implementation, compileOnly, runtimeOnly Dependencies in Kotlin Multiplatform sourceSets { commonMain.dependencies { implementation(libs.kotlinx.coroutines.core) } jsMain.dependencies { implementation(libs.kotlinx.coroutines.core-js) } } 

Kotlin Budapest Meetup I 2024 You can set them at: • Source set level • Top level api, implementation, compileOnly, runtimeOnly Dependencies in Kotlin Multiplatform dependencies { commonMainImplementation(libs.kotlinx.coroutines.core) jsMainImplementation(libs.kotlinx.coroutines.core-js) } 

Kotlin Budapest Meetup I 2024 You can set them at: • Source set level • Top level You can add dependencies on: • Kotlin library api, implementation, compileOnly, runtimeOnly Dependencies in Kotlin Multiplatform sourceSets { commonMain.dependencies { implementation(kotlin("stdlib")) } commonTest.dependencies { implementation(kotlin("test")) } } 

Kotlin Budapest Meetup I 2024 You can set them at: • Source set level • Top level You can add dependencies on: • Kotlin library api, implementation, compileOnly, runtimeOnly Dependencies in Kotlin Multiplatform sourceSets { commonMain.dependencies { implementation(kotlin("stdlib")) } commonTest.dependencies { implementation(kotlin("test")) } } 

Kotlin Budapest Meetup I 2024 You can set them at: • Source set level • Top level You can add dependencies on: • Kotlin library • Kotlin Multiplatform library api, implementation, compileOnly, runtimeOnly Dependencies in Kotlin Multiplatform sourceSets { commonMain.dependencies { implementation(libs.kotlinx.serialization.json) } } 

Kotlin Budapest Meetup I 2024 You can set them at: • Source set level • Top level You can add dependencies on: • Kotlin library • Kotlin Multiplatform library • Platform-specific library api, implementation, compileOnly, runtimeOnly Dependencies in Kotlin Multiplatform sourceSets { androidMain.dependencies { implementation(libs.retrofit) } } 

Kotlin Budapest Meetup I 2024 You can set them at: • Source set level • Top level You can add dependencies on: • Kotlin library • Kotlin Multiplatform library • Platform-specific library • Kotlin Multiplatform project api, implementation, compileOnly, runtimeOnly Dependencies in Kotlin Multiplatform sourceSets { commonMain.dependencies { api(projects.core) } } 

Kotlin Budapest Meetup I 2024 • Compatible targets • Versions are aligned through source sets Dependency resolution Dependencies in Kotlin Multiplatform 

Kotlin Budapest Meetup I 2024 • Compatible targets • Versions are aligned through source sets Dependency resolution Dependencies in Kotlin Multiplatform kermit:2.0.0 commonMain kermit:2.0.0 androidMain kermit:2.0.0 iosMain 

Kotlin Budapest Meetup I 2024 • Compatible targets • Versions are aligned through source sets Dependency resolution Dependencies in Kotlin Multiplatform kermit:2.0.0 commonMain kermit:2.0.0 kermit:2.0.4 anAndroidLibrary:1.0.0 androidMain kermit:2.0.0 iosMain 

Kotlin Budapest Meetup I 2024 • Compatible targets • Versions are aligned through source sets Dependency resolution Dependencies in Kotlin Multiplatform kermit:2.0.0 kermit:2.0.4 commonMain kermit:2.0.0 kermit:2.0.4 anAndroidLibrary:1.0.0 androidMain kermit:2.0.0 kermit:2.0.4 iosMain 

Kotlin Budapest Meetup I 2024 Platform-specific dependencies 

Kotlin Budapest Meetup I 2024 • The same Android Platform-specific dependencies sourceSets { androidMain.dependencies { implementation(libs.androidx.lifecycle.viewmodel) } } 

Kotlin Budapest Meetup I 2024 • npm() function Kotlin/JS Platform-specific dependencies sourceSets { jsMain.dependencies { implementation(npm(“is-sorted”, ”1.0,5”)) } } 

Kotlin Budapest Meetup I 2024 • npm() function • External declarations Kotlin/JS Platform-specific dependencies @JsModule("is-sorted") @JsNonModule external fun sorted(a: Array): Boolean 

Kotlin Budapest Meetup I 2024 • Definition file .def • Properties Kotlin/Native Platform-specific dependencies headers = curl/curl.h headerFilter = curl/* compilerOpts.linux = -I/usr/include -I/usr/include/x86_64-linux-gnu linkerOpts.osx = -L/opt/local/lib -L/usr/local/opt/curl/lib -lcurl linkerOpts.linux = -L/usr/lib/x86_64-linux-gnu -lcurl 

Kotlin Budapest Meetup I 2024 • Cocoapods • (SPM) iOS Platform-specific dependencies cocoapods { summary = "Some description for the Shared Module" homepage = "Link to the Shared Module homepage" version = "1.0" ios.deploymentTarget = "16.0" podfile = project.file("../iosApp/Podfile") framework { baseName = "shared" isStatic = true } pod("FirebaseAuth") { version = "10.16.0" } } 

Kotlin Budapest Meetup I 2024 • Cocoapods • cinterop iOS Platform-specific dependencies MyFramework.def language = Objective-C modules = MyFramework package = MyFramework 

Kotlin Budapest Meetup I 2024 • Cocoapods • cinterop iOS Platform-specific dependencies iosArm64 { val main by compilations.getting { val MyFramework by cinterops.creating { definitionFile.set(project.file("src/nativeInterop/cinterop/MyFramework.def")) compilerOpts("-framework", "MyFramework", "-F/path/to/framework/") } } binaries.all { linkerOpts("-framework", "MyFramework", "-F/path/to/framework/") } } 

Kotlin Budapest Meetup I 2024 Common issues 

Kotlin Budapest Meetup I 2024 cocoapods { pod("Socket.IO-Client-Swift") { version = "16.1.1” moduleName = "SocketIO" } } Swift-only library Common Issues :shared:iosArm64Main: cinterop file: /Users/tfabian/AndroidStudioProjects/Couchbase/shared/build/c lasses/kotlin/iosArm64/main/cinterop/ shared-cinterop-SocketIO.klib does not exist Possible solution: - Declare repository providing the artifact, see the documentation at https://docs.gradle.org/current/userguide/declaring_repositories .html Error 

Kotlin Budapest Meetup I 2024 cocoapods { pod("Socket.IO-Client-Swift") { version = "16.1.1” moduleName = "SocketIO" } } Swift-only library Common Issues @objc public class SocketIo: NSObject { @objc public func connect() { socket.connect() } @objc public func disconnect() { socket.disconnect() } ... } Solution 

Kotlin Budapest Meetup I 2024 sourceSets { commonMain.dependencies { api(libs.kotlinx.serialization.json) } } Transitive dependencies Common Issues java.lang.NoClassDefFoundError: Failed resolution of: Lkotlinx/serialization/json/JsonKt Error 

Kotlin Budapest Meetup I 2024 sourceSets { commonMain.dependencies { api(libs.kotlinx.serialization.json) } } Transitive dependencies Common Issues kotlin { ios.binaries.framework { export(libs.kotlinx.serialization.json) // OR transitiveExport = true } } Solution 

Kotlin Budapest Meetup I 2024 cocoapods { pod("Socket.IO-Client-Swift") { version = "16.1.1” moduleName = "SocketIO" } } @import directives Common Issues Exception in thread "main" java.lang.Error: /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSi mulator18.0.sdk/usr/include/copyfile.h:35:10: fatal error: 'sys/cdefs.h' file not found … /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSi mulator18.0.sdk/System/Library/Frameworks/CFNetwork.framework/Headers/CFNetwork.h:18:10: fatal error: could not build module 'CoreFoundation’ /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSi mulator18.0.sdk/usr/include/xpc/xpc.h:6:10: fatal error: could not build module 'os_object’ at org.jetbrains.kotlin.native.interop.indexer.ModuleSupportKt.getModulesASTFiles(ModuleSupport.kt:80) at org.jetbrains.kotlin.native.interop.indexer.ModuleSupportKt.getModulesInfo(ModuleSupport.kt:15) at org.jetbrains.kotlin.native.interop.gen.jvm.MainKt.buildNativeLibrary(main.kt:564) at org.jetbrains.kotlin.native.interop.gen.jvm.MainKt.processCLib(main.kt:308) at org.jetbrains.kotlin.native.interop.gen.jvm.MainKt.processCLibSafe(main.kt:244) at org.jetbrains.kotlin.native.interop.gen.jvm.MainKt.access$processCLibSafe(main.kt:1) at org.jetbrains.kotlin.native.interop.gen.jvm.Interop.interop(main.kt:102) at org.jetbrains.kotlin.cli.utilities.InteropCompilerKt.invokeInterop(InteropCompiler.kt:49) at org.jetbrains.kotlin.cli.utilities.MainKt.mainImpl(main.kt:23) at org.jetbrains.kotlin.cli.utilities.MainKt.main(main.kt:44) Error 

Kotlin Budapest Meetup I 2024 cocoapods { pod("Socket.IO-Client-Swift") { version = "16.1.1” moduleName = "SocketIO" } } @import directives Common Issues extraOpts += listOf("-compiler-option", "-fmodules") Solution 

Kotlin Budapest Meetup I 2024 cocoapods { pod("Socket.IO-Client-Swift") { version = "16.1.1” } } Dash in cocoapod’s name Common Issues fatal error: module 'socket_io_wrapper' not found Error 

Kotlin Budapest Meetup I 2024 cocoapods { pod("Socket.IO-Client-Swift") { version = "16.1.1” } } Dash in cocoapod’s name Common Issues moduleName = "SocketIO" Solution 

Kotlin Budapest Meetup I 2024 cocoapods { pod("StripePaymentsUI") { version = ”23.31.1" } } Pod::Spec.new do |s| s.name = 'StripePaymentsUI’ ... s.dependency 'StripeCore', s.version.to_s s.dependency 'StripeUICore', s.version.to_s s.dependency 'StripePayments', s.version.to_s end Linked modules Common Issues Unresolved reference: STPPaymentHandlerActionStatus Error 

Kotlin Budapest Meetup I 2024 cocoapods { pod("StripePaymentsUI") { version = ”23.31.1" } } Linked modules Common Issues pod("StripePayments") { version = ”23.31.1" } Solution 

Kotlin Budapest Meetup I 2024 sourceSets { commonMain.dependencies { implementation(libs.google.gson) } } Dependency at the wrong place Common Issues Nothing :( Error 

Kotlin Budapest Meetup I 2024 sourceSets { commonMain.dependencies { implementation(libs.google.gson) } } Dependency at the wrong place Common Issues androidMain • Remember what you’ve learned. • KT-72287 Improve error reporting when dependency doesn't match expected platforms Solution 

Kotlin Budapest Meetup I 2024 Libraries’ libraries 

Kotlin Budapest Meetup I 2024 Libraries’ libraries 

Kotlin Budapest Meetup I 2024 Libraries’ libraries 

Kotlin Budapest Meetup I 2024 Libraries’ libraries 

Kotlin Budapest Meetup I 2024 Libraries’ libraries 

Kotlin Budapest Meetup I 2024 Thank you. 

Kotlin Budapest Meetup. I 2024 Get in Touch LinkedIn in/tamas--fabian X @tomi_fabian GitHub github.com/TomiFabian 

Kotlin Budapest Meetup I 2024 • https://kotlinlang.org/docs/multiplatform-intro.html • https://github.com/JetBrains/kotlin • https://github.com/JakeWharton/mosaic • https://stackoverflow.com/questions/tagged/kotlin-multiplatform • https://youtrack.jetbrains.com/issues/KT References