What is Kotlin Multiplatform: Overview and Example

Kotlin Multiplatform is a technology that lets you write code once and run it on multiple platforms like Android, iOS, and the web. It shares common logic while allowing platform-specific code where needed.

How It Works

Kotlin Multiplatform works like a shared toolbox for different platforms. Imagine you have a recipe book that you want to use in different kitchens: one in your home, one at a friend's house, and one in a restaurant. Instead of writing the recipe again for each kitchen, you write it once and adapt only the parts that depend on the kitchen's tools.

In Kotlin Multiplatform, you write common code for things like data handling, business rules, or networking. Then, you write small pieces of platform-specific code for things like user interface or device features. The Kotlin compiler helps combine these parts so your app works on Android, iOS, desktop, or web without rewriting the shared logic.

Example

This example shows a simple Kotlin Multiplatform function that returns a greeting message. The common code defines the function, and platform-specific code can call it.

kotlin

expect fun platformName(): String

fun greet(): String {
    return "Hello from ${platformName()}!"
}

// Android implementation
actual fun platformName(): String = "Android"

// iOS implementation
actual fun platformName(): String = "iOS"

Output

Hello from Android!
Hello from iOS!

When to Use

Use Kotlin Multiplatform when you want to share code between apps on different platforms to save time and keep logic consistent. It is great for projects that need to run on Android and iOS, or even desktop and web, without duplicating business logic.

For example, if you are building a chat app, you can share message handling, data storage, and network code, while writing separate user interfaces for each platform. This approach reduces bugs and speeds up development.

Key Points

• Kotlin Multiplatform shares common code across platforms.
• Platform-specific code handles unique features or UI.
• It reduces duplication and keeps apps consistent.
• Supports Android, iOS, desktop, and web.

Key Takeaways

Kotlin Multiplatform lets you write shared code for multiple platforms.

It separates common logic from platform-specific parts.

Use it to save time and keep your app consistent across devices.

It supports Android, iOS, desktop, and web targets.