The document discusses Kotlin Multiplatform Mobile (KMM), which allows sharing code across Android and iOS platforms. It provides an overview of what KMM is and isn't, how it works using expect/actual keywords and interfaces, integration methods, requirements, documentation, sample projects, libraries, benefits and challenges. Key points are that KMM allows a single codebase for business logic across platforms, saves development time, provides a single source of truth, but concurrency and debugging can be challenging.

1. Still Sleeping
on KMM?
@emmakoko96

2. Who am I?
Emmanuel Kehinde
Mobile Engineer @Plume
Blog @emmanuelkehinde.io
...
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3. Still Sleeping on Kotlin
Multiplatform Mobile?
@emmakoko96

4. Kotlin Multiplatform
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5. Kotlin Multiplatform
Single codebase for the business logic of your apps
across multiple platforms, in pure kotlin.
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6. Single codebase for the business
logic of your apps across multiple
platforms, in pure kotlin.
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7. Kotlin Multiplatform
Mobile
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8. Kotlin Multiplatform Mobile
Sharing mobile native code (Android, iOS)
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9. Sharing mobile native code
(Android, iOS)
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10. What KMM is
not
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11. KMM is not
→ "cross-platform"
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12. KMM is not
→ "cross-platform"
→ Common UI
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13. KMM is not
→ "cross-platform"
→ Common UI
→ Dependent on a UI Toolkit
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14. KMM is not
→ "cross-platform"
→ Common UI
→ Dependent on a UI Toolkit
→ Operating System Specific
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15. What does it
look like?
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16. Similar to a regular Java/Kotlin Module
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17. Similar to a regular Java/Kotlin
Module
TwittaSave: https://github.com/emmanuelkehinde/
TwittaSave-Mobile

18. expect/actual keywords
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19. // CommonMain
expect class TwitterApiLogger() : TwitterLogger {
override fun log(message: String)
}
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20. // CommonMain
expect class TwitterApiLogger() : TwitterLogger {
override fun log(message: String)
}
// AndroidMain
actual class TwitterApiLogger: TwitterLogger {
actual override fun log(message: String) {
if (BuildConfig.DEBUG) {
Log.d("Network", message)
}
}
}
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21. // CommonMain
expect class TwitterApiLogger() : TwitterLogger {
override fun log(message: String)
}
// iOSMain
actual class TwitterApiLogger: TwitterLogger {
actual override fun log(message: String) {
if (Platform.isDebugBinary) {
NSLog("%s", message)
}
}
}
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22. A better alternative - Interface
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23. // Common
interface TwitterCredentialsProvider {
var bearerToken: String
val consumerKey: String
val consumerSecret: String
}
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24. // Common
interface TwitterCredentialsProvider {
var bearerToken: String
val consumerKey: String
val consumerSecret: String
}
// androidApp
object TwitterCredentialsDataProvider : TwitterCredentialsProvider {
override var bearerToken: String = String()
override val consumerKey: String
get() = BuildConfig.CONSUMER_KEY
override val consumerSecret: String
get() = BuildConfig.CONSUMER_SECRET
}
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25. // Common
interface TwitterCredentialsProvider {
var bearerToken: String
val consumerKey: String
val consumerSecret: String
}
// iOSApp
class TwitterCredentialsDataProvider: TwitterCredentialsProvider {
static let shared: TwitterCredentialsProvider = TwitterCredentialsDataProvider()
private let infoDict: [String: Any]?
init() {
infoDict = Bundle.main.infoDictionary
}
var bearerToken: String = String()
var consumerKey: String {
return (infoDict?["TWITTER_CONSUMER_KEY"] as? String) ?? String()
}
var consumerSecret: String {
return (infoDict?["TWITTER_CONSUMER_SECRET"] as? String) ?? String()
}
}
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26. Benefits of Interface
→ Platform specific code can be easily managed
→ Testing is easier as you can mock easily
→ Useful when handling concurrency with Kotlin
Native
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27. Integration
Methods
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28. Android
Module/Library integration
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29. iOS
→ XCFramework
→ Cocoapods
→ Swift Package
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30. Getting
Started with
KMM
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31. Requirements
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32. Requirements
→ Computer running MacOS, Windows or Linux
→ Android Studio 4.2 or later
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33. KMM Documentation
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35. Android Studio Plugin
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41. Refactoring Existing
Project
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42. Community
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43. Community
→ Open source sample projects
(DroidconKotlin, PeopleInSpace, etc.)
Sample Projects - https://kotlinlang.org/docs/mobile/samples.html

44. Community
→ Open source sample projects
(DroidconKotlin, PeopleInSpace, etc.)
→ Kotlin Slack
Join Kotlin Slack - https://surveys.jetbrains.com/s3/kotlin-slack-sign-up

45. Community
→ Open source sample projects
(DroidconKotlin, PeopleInSpace, etc.)
→ Kotlin Slack
→ Kotlin issue tracker (YouTrack)
Kotlin Issue Tracker - https://youtrack.jetbrains.com/issues/KT

46. Community
→ Open source sample projects
(DroidconKotlin, PeopleInSpace, etc.)
→ Kotlin Slack
→ Kotlin issue tracker (YouTrack)
→ Github issues/releases
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47. KMM Libraries
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48. KMM Libraries
→ Ktor for network requests
→ Coroutines for asynchronous programming
→ SQLDelight for data storage
and lots more...
KMM Libraries - https://libs.kmp.icerock.dev/

49. The Good
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50. The Good
→ Natively Integrated
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51. The Good
→ Natively Integrated
→ Saves time
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52. The Good
→ Natively Integrated
→ Saves time
→ Single source of truth
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53. The not so
Good
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54. The not so Good
→ Concurrency/Memory Management not fun
Blog Post: https://emmanuelkehinde.io/supporting-multithreaded-coroutines-in-a-kotlin-multiplatform-project

55. The not so Good
→ Concurrency/Memory Management not fun
→ Debugging from Xcode still a concern
Xcode Plugin: https://github.com/touchlab/xcode-kotlin

56. My Opinion?
@emmakoko96

57. Consider your team, project size and long term
maintenance
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58. More Helpful Resources
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59. More Helpful Resources
→ https://kotlinlang.org/docs/mobile/home.html
→ https://emmanuelkehinde.io/category/kotlin-
multiplatform/
→ https://github.com/emmanuelkehinde/
TwittaSave-Mobile
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60. Thanks!
Twitter - @emmakoko96