Created by JetBrains to enable using Kotlin to build iOS and Android apps with native UI from a single codebase, Kotlin Multiplatform Mobile has exited the experimental phase and is now available in beta.
Kotlin Multiplatform Mobile is an SDK for iOS and Android app development that allows you to maintain a shared codebase for networking, data storage, and analytics, as well as the other logic of your Android and iOS apps.
During the experimental phase JetBrains tried multiple approaches to memory management, libraries, and project configuration and refined the balance between cross-platform features, including networking, data storage, and analytics, and access to the native SDKs.
Specifically, Kotlin Multiplatform Mobile beta implements a native automatic memory manager that aims to simplify sharing objects between threads by providing lock-free concurrent programming primitives.
According to JetBrains, the beta release provides enough stability for developers to start adopting Kotlin Multiplatform Mobile. As a sign of its readiness for adoption, JetBrains highlights the growing multiplatform library ecosystem, community support, and especially a number of early adopters' case studies, which include Autodesk, VMware, Netflix, and many more.
Furthermore, a number of popular libraries have already adopted Kotlin Multiplatform, including async event handling framework Ktor, typesafe SQL API generator SQLDelight, GraphQL client Apollo, and dependency injection framework Koin.
Kotlin Multiplatform is integrated with Android Studio, leveraging tooling and ecosystem familiar to Android developers, whereas iOS developers will surely have a somewhat less gradual learning curve. While Android Studio is the main IDE for Kotlin Multiplatform development, Xcode will still be required to build iOS apps and submit them to the App Store.
At the moment of this writing, the Kotlin Multiplatform Mobile plugin is still at an alpha stage. The Kotlin Multiplaform plugin provides a collection of directives to use in Gradle files, including new targets for the iOS, watchOS, and tvOS platforms, sourceSet, compilation, and others.
If you prefer a different approach, you can also use Kotlin Multiplatform to create cross-platform libraries() and then use them within your independent iOS and Android projects.
You can find here a curated list of Kotlin Multiplatform Mobile samples.