Creating SDKs in Kotlin Multiplatform | Devfest Pune

Kotlin Multiplatform or KMP is the talk of the town nowadays. Everyone is talking about it, lots of big orgs are using it as well, including Thoughtworks, Shopify, JioCinema, Cred etc.
While making the whole app with KMP (Kotlin Multiplatform) sounds fantastic, another really good use case would be to migrate your SDKs and libraries to KMP.
Whether you're a B2B company that offers SDKs and libraries to external clients or creating and using SDKs internally within your company, making it in KMP can help ensure consistency among different platforms, less time and effort spent, and in the end lower cost of maintenance.
In this talk, we'll discuss why and how you should create SDKs and migrate existing SDKs to KMP, and some best practices regarding the same, from a person who has done it in production, affecting millions of users.
In this session, we'll learn the following
- Why Kotlin Multiplatform for SDKs
- Difference between multiplatform and cross-platform
- How to support different platforms (Android, iOS, JS, Flutter etc.) when creating SDKs
- Performance optimization and handling threading for different platforms
- Best practices

Learn why and how to migrate or create new SDKs / libraries with Kotlin Multiplatform.
In this session, we'll learn the following
- Why Kotlin Multiplatform for SDKs
- Difference between multiplatform and cross-platform
- How to support different platforms (Android, iOS, JS, Flutter etc.) when creating SDKs
- Performance optimization and handling threading for different platforms
- Best practices

Transcript

1. Creating SDKs with Kotlin Multiplatform Rivu Chakraborty 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social https://courses.rivu.dev/
2. • India’s first GDE (Google Developer Expert) for • More than 11 years in the Industry • Mobile Architect @ JioCinema • Previously ◦ Byju’s ◦ Paytm ◦ Gojek ◦ Meesho • Author (wrote multiple Kotlin books) • Speaker • Mentor • Community Person • YouTuber (?) 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Who am I? 󰞦
4. What’s an SDK?
5. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social What’s an SDK? 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Software Development Kit. Library/SDK
6. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social What’s an SDK? 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Software Development Kit. Library/SDK
7. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social What’s an SDK? 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social A code block, that helps your or client apps reduce redundancy, by using this library / SDK
8. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Most Common SDK Use Cases 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social • Analytics • Chat / Conversation • Ads • Image Processing • Audio-Video Processing
9. Rules for Developing SDK
10. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social
11. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social SDK Rules 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social 0. Should be Plug and Play
12. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social SDK Rules 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social 0. Should be Plug and Play 1. Should be easy to remove
13. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social SDK Rules 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social 0. Should be Plug and Play 1. Should be easy to remove 2. Should not add unnecessary extra dependencies to the client app
14. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social SDK Rules 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social 0. Should be Plug and Play 1. Should be easy to remove 2. Should not add unnecessary extra dependencies to the client app 3. Interaction should be straightforward for the client
15. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social SDK Rules 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social 0. Should be Plug and Play 1. Should be easy to remove 2. Should not add unnecessary extra dependencies to the client app 3. Interaction should be straightforward for the client 4. Data Types should be interoperable
16. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social SDK Rules 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social 0. Should be Plug and Play 1. Should be easy to remove 2. Should not add unnecessary extra dependencies to the client app 3. Interaction should be straightforward for the client 4. Data Types should be interoperable 5. [Optional] Should allow client apps to implement own UI
17. Building an SDK
18. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Building an SDK 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social • Hire / Allocate Developers • Define Requirements • Plan Roadmap • Develop, maintain and test SDK integration • Cross Check Parity / Consistency across platforms • Setup SDK release • Maintain versioning across platforms
19. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Building an SDK 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social • Hire / Allocate Developers • Define Requirements • Plan Roadmap • Develop, maintain and test SDK integration • Cross Check Parity / Consistency across platforms • Setup SDK release • Maintain versioning across platforms Android 1x
20. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Building an SDK 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social • Hire / Allocate Developers • Define Requirements • Plan Roadmap • Develop, maintain and test SDK integration • Cross Check Parity / Consistency across platforms • Setup SDK release • Maintain versioning across platforms Android, iOS 2x
21. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Building an SDK 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social • Hire / Allocate Developers • Define Requirements • Plan Roadmap • Develop, maintain and test SDK integration • Cross Check Parity / Consistency across platforms • Setup SDK release • Maintain versioning across platforms Android, iOS, Web 3x
22. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Building an SDK 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social • Hire / Allocate Developers • Define Requirements • Plan Roadmap • Develop, maintain and test SDK integration • Cross Check Parity / Consistency across platforms • Setup SDK release • Maintain versioning across platforms Android, iOS, Web, tvOS ~4x
23. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Building an SDK 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social • Hire / Allocate Developers • Define Requirements • Plan Roadmap • Develop, maintain and test SDK integration • Cross Check Parity / Consistency across platforms • Setup SDK release • Maintain versioning across platforms Android, iOS, Web, tvOS, Tizen & WebOS [HTML5 TV] ~5x
24. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Building an SDK 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social • Hire / Allocate Developers • Define Requirements • Plan Roadmap • Develop, maintain and test SDK integration • Cross Check Parity / Consistency across platforms • Setup SDK release • Maintain versioning across platforms Android, iOS, Web, tvOS, Tizen & WebOS [HTML5 TV], WatchOS, WearOS ~7x
25. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social
26. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Solution? 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Share Code across all Platforms
27. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Solution? 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Share Code across all Platforms
28. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Share Code across all Platforms 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social
29. Current Solutions for Sharing Code across Platforms
30. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Flutter 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social React Native Kotlin Multiplatform C/C++
31. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Flutter 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social 0. Should be Plug and Play 1. Should be easy to remove 2. Should not add unnecessary extra dependencies to the client app 3. Interaction should be straightforward for the client 4. Data Types should be interoperable 5. [Optional] Should allow client apps to implement own UI
32. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social React Native 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social 0. Should be Plug and Play 1. Should be easy to remove 2. Should not add unnecessary extra dependencies to the client app 3. Interaction should be straightforward for the client 4. Data Types should be interoperable 5. [Optional] Should allow client apps to implement own UI
33. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social 0. Should be Plug and Play 1. Should be easy to remove 2. Should not add unnecessary extra dependencies to the client app 3. Interaction should be straightforward for the client 4. Data Types should be interoperable 5. [Optional] Should allow client apps to implement own UI ✓ C/C++
34. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Too Complicated to work with. Unless necessary. C/C++
35. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Kotlin Multiplatform 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social 0. Should be Plug and Play 1. Should be easy to remove 2. Should not add unnecessary extra dependencies to the client app 3. Interaction should be straightforward for the client 4. Data Types should be interoperable 5. [Optional] Should allow client apps to implement own UI ✓
36. Why Kotlin Multiplatform [KMP/KMM]
37. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social • Developed by Jetbrains • Open Source • Supported by Google for Android Development • Supported by Spring for Server • Has own framework (Ktor) for asynchronous client and server applications • Has different targets for Different platforms. e.g. Kotlin/JVM, Kotlin/Native, Kotlin/JS, Kotlin/Wasm etc.
38. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Kotlin Multiplatform
39. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Kotlin Multiplatform 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Using Kotlin Code in projects to target more than one platform
40. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Kotlin Multiplatform 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social • Idiomatic Kotlin Language for all platforms • Low Risk ◦ You decide what to share, what not ◦ Option to use existing 3rd party libraries for each platform • Interoperability • Consistency across platforms • Export platform native SDK builds • Strong Community Support
41. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Current users of KMP 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social
42. Understanding Kotlin Multiplatform [KMP/KMM]
43. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social
44. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social The Structure 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social
45. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social The Structure 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Common JVM JS Native Android Server Apple Linux mingw iOS tvOS watchOS macOS linux_x64 linux_arm64 mingx64 iosX64 iosArm64 iosSimulatorArm64 tvosX64 tvosArm64 tvosSimulatorArm64 macosX64 macosArm64 watchosX64 watchosArm32 watchosArm64 watchosSimulatorArm64 watchosDeviceArm64
46. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social The Structure expect fun doSomething() actual fun doSomething() { //Platform specific logic here }
47. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social The Structure Directory Structure
48. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Expect/Actual expect fun getRandomUUID(): String commonMain
49. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Expect/Actual androidMain actual fun getRandomUUID(): String = UUID.randomUUID().toString()
50. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Expect/Actual iosMain actual fun getRandomUUID(): String = NSUUID().UUIDString()
51. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Expect/Actual jsMain import uuid actual fun getRandomUUID(): String = uuid.v4().toString()
52. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Dependency Management val commonMain by getting { dependencies { implementation(libs.bundles.common.ktor) implementation(libs.coroutines.core) implementation(libs.kotlinx.datetime) implementation(libs.koin.core) implementation(libs.skie) } }
53. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Dependency Management val jsMain by getting { dependencies { implementation(npm("uuid", "9.0.0")) implementation(libs.wire.runtime.js) } }
54. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Dependency Management val androidMain by getting { dependencies { implementation(libs.ktor.client.okHttp) implementation(libs.okhttp.loggingInterce ptor) implementation(libs.koin.android) implementation(libs.sqlDelight.android) } }
55. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social val iosMain by getting { dependencies { implementation(libs.ktor.client.darwin) implementation(libs.sqlDelight.native) } } Dependency Management
56. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Shared Common Code class EventsRepository( private val eventsRemoteDS: EventsRemoteDS, private val eventsLocalDS: EventsLocalDS, ) { suspend fun trackEvent( eventData: EventData, eventName: String, ) { //Logic to track Events ... } }
57. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Exported SDK files Android .aar iOS .xcframework JS Minified js / NPM
58. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Setting up iOS Distribution XCFramework val xcFramework = XCFramework("IndiaConferences") listOf( iosX64(), iosArm64(), iosSimulatorArm64(), ).forEach { it.binaries.framework { xcFramework.add(this) baseName = SDKConfig.sdkName } }
59. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social SPM kmmbridge { spm() mavenPublishArtifacts() versionPrefix.set(SDKConfig.version) frameworkName.set(SDKConfig.sdkName) } https://kmmbridge.touchlab.co Setting up iOS Distribution
60. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Taking care of Interoperability https://skie.touchlab.co/ data class User @DefaultArgumentInterop.Enabled constructor( val id: String, val firstName: String, val lastName: String, val userType: UserType = UserType.User ) @EnumInterop.Enabled enum class UserType { User, Admin, }
61. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social https://skie.touchlab.co/ data class User @DefaultArgumentInterop.Enabled constructor( val id: String, val firstName: String, val lastName: String, val userType: UserType = UserType.User ) @EnumInterop.Enabled enum class UserType { User, Admin, } @JsExport object UserTypeJS { val User = UserType.User val Admin = UserType.Admin } Taking care of Interoperability
62. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Versioning object LibraryConfig { val version = "1.0.0" const val groupId = "dev.rivu.kmp.sdkDemo" const val artifactIdSdk = "core" val sdkName = "demo-sdk" }
63. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Reducing Size in JS js { browser { dceTask { keep("shared.dev.rivu.MyClass") } binaries.executable() } }
64. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Using the bundle in JS
65. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social Using the XCFramework in iOS
66. IDEs and Tools
67. 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social IDEs and Tools
68. Resources • https://speakerdeck.com/aldefy/a-hitchhikers-guide-to-kotlin-multiplatform • https://github.com/joreilly/PeopleInSpace • https://github.com/joreilly/Confetti • https://kotlinlang.org/docs/multiplatform.html • https://courses.rivu.dev • https://leanpub.com/thecomposebook
69. Thank You Rivu Chakraborty 🌐https://www.rivu.dev/ youtube.com/@rivutalks @rivuchakraborty @rivu@androiddev.social https://courses.rivu.dev/