Seamless integration with existing codebases

1An SDK, not a framework

Kotlin's philosophy is that you don't have to migrate the entire application. Start with a single module or feature, see how it goes, and then gradually move other parts as you see fit.

2Reuse your business logic

Use the Kotlin code you have already written, and modify it to be compatible with iOS. You’ll get less code and fewer bugs, and share domain knowledge between your iOS and Android developers.

3Smooth interoperability with platform- specific code

Whenever a task cannot be solved in common code, use the expect/actual pattern to seamlessly write platform-specific code.

Cross-platform without the usual overhead

4Have a native UI

Kotlin does not impose any restrictions on how you develop your app’s UI. Its appearance, behavior, and performance all remain native.

5No lagging behind native platforms

Write platform-native logic and easily use it in your Kotlin code – don’t wait until vendors or the mobile community add support for new native features such as:

6Use the language you already know and love

Go cross-platform without introducing any new languages to your codebase.

class APIClient {fun getUserInfo(userId: String): Userfun searchUsers(userName: String): List<User>}

class SearchPresenter {val client = APIClient()fun findUsersByName(name: String): List<User> {val users = client.searchUsers(name)return users}}

class UserViewModel {let client = APIClient()func getUserAge(userId: String) -> Int {let user = client.getUserInfo(userId: userId)return user.age}}

expect fun String.dateFormatToMilliseconds(format: String): Long

actual fun String.dateFormatToMilliseconds(format: String): Long=SimpleDateFormat(format, Locale.getDefault()).parse(this).time

actual fun String.dateFormatToMilliseconds(format: String): Long {val formatter = NSDateFormatter()formatter.dateFormat = parseFormatreturn formatter.dateFromString(this)?.timeIntervalSince1970?.toLong()?: throw Exception("Failed, to parse $this for format $parseFormat")}

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data class Product(val name: String, val price: Int)fun List<Product>.checkOut() {val totalPrice = sumBy { it.price }val allPositions = joinToString(separator = " and ") { it.name }println("You've bought $allPositions for $totalPrice coins!")}

Teams that use Kotlin Mobile Multiplatform in production

Quizlet

Quizlet is a product that helps people practice and master whatever they're trying to learn. We use Kotlin Multiplatform to share business logic across our iOS, Android, and web clients for our 50+ million active monthly users.

Using Kotlin Multiplatform lets us focus on innovating in learning, instead of spending time rewriting the same code for each platform. MPP works much better for us than our previous attempts at sharing code, because it treats each platform as a first-class target, rather than relying on brittle workarounds or bridge layers.

Ankush Gupta, Senior Software Engineer