How do you ensure your Kotlin code works on all platforms?

1 Choose the right project structure

Depending on your project's scope and goals, you can choose between two main approaches to structure your Kotlin multiplatform project: hierarchical or parallel. Hierarchical projects have a single common source set that contains the shared logic and dependencies, and then platform-specific source sets that inherit from the common one and override or extend it as needed. Parallel projects have separate source sets for each platform, and a common source set that contains only the interfaces or abstractions that the platform-specific code implements. Both approaches have pros and cons, so you should consider factors such as code reuse, maintainability, testing, and performance.

2 Use Kotlin Multiplatform Mobile

Kotlin Multiplatform Mobile (KMM) is a plugin and a set of libraries that simplify the development of cross-platform mobile applications with Kotlin. KMM allows you to share business logic, data models, network communication, and other common features between Android and iOS, while still using the native UI frameworks and tools for each platform. KMM also provides tools for testing, debugging, and deploying your multiplatform mobile code. To use KMM, you need to install the plugin in your IDE, configure your Gradle build files, and create the shared and platform-specific modules.

4 Use common libraries and frameworks

Kotlin's cross-platform development capabilities are bolstered by the availability of common libraries and frameworks that work across multiple platforms. These libraries and frameworks can help with tasks such as networking, serialization, concurrency, testing, or dependency injection. Some of the most popular ones are Ktor, a lightweight and asynchronous framework for web applications and clients; kotlinx.serialization, a library for serializing and deserializing data in various formats; kotlinx.coroutines, a library for managing concurrency and asynchronous operations with coroutines; Koin, a pragmatic and lightweight dependency injection framework; and Kotest, a flexible and expressive testing framework with multiple styles and features.

5 Follow best practices and guidelines

To ensure your Kotlin code works on all platforms, you should follow some best practices and guidelines that can help you avoid common pitfalls and errors. For example, using expect and actual declarations to define common interfaces and implement them differently on each platform; using @SharedImmutable and @ThreadLocal annotations to mark shared state and thread-local state respectively; using platform-specific APIs only when necessary and wrapping them in common abstractions or extensions; utilizing Gradle's source sets and dependencies configuration to organize and manage your code and libraries; and adhering to Kotlin's coding conventions and style guides to write consistent and readable code.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?