UniFFI Kotlin Multiplatform Bindings¶

A Gradle plugin and binding generator that turns a Rust library into a Kotlin Multiplatform library, using Mozilla's UniFFI.

You annotate your Rust code with UniFFI's macros (or describe it in a UDL file). The plugin then builds the crate for every Kotlin target in your project, generates Kotlin bindings for it, and wires the bindings and native libraries into the right source sets. Your Kotlin code calls the Rust functions from commonMain. The plugin handles the rest.

#[uniffi::export]
pub fn add(a: i32, b: i32) -> i32 {
    a + b
}

import com.example.quickstart.add

add(2, 2) // 4

Supported targets¶

Kotlin target	How Rust is called
jvm()	JNA, dynamic library bundled as a resource
android { }	JNA, dynamic library bundled as jniLibs
iosArm64(), iosSimulatorArm64(), iosX64(), macosArm64()	cinterop, static library
linuxX64(), linuxArm64()	cinterop, static library
mingwX64()	cinterop, static library

Where to go from here¶

If you want to use the plugin, start with the user guide. It sets up a small project first, and then goes through the features one by one: what you write in Rust, the Kotlin you get, and the configuration involved.

If you want to work on the plugin itself, read the internals. They explain how the Gradle plugin, the binding generator and the runtime fit together, and cover the parts of UniFFI you need to know to change them.

Relation to other projects¶

This project started as a fork of UniFFI Kotlin Multiplatform Bindings by Trixnity, and has been largely rewritten since.

Gobley is another project with the same goal. See Comparison with other projects for how the two differ.

This project is used in production, for example in the Kapun SDK. Please report problems in the issue tracker.