The UniFFI plugin

💡 We recommend to first read the UniFFI user guide.

The UniFFI plugin is responsible for generating Kotlin bindings from your Rust package. Here is an example of using the UniFFI plugin to build bindings from the resulting library binary.

import gobley.gradle.Variant
import gobley.gradle.rust.targets.RustAndroidTarget

plugins {
    kotlin("multiplatform")
    id("dev.gobley.cargo") version "0.2.0"
    id("dev.gobley.uniffi") version "0.2.0"
}

uniffi {
    // Generate the bindings using library mode.
    generateFromLibrary {
        // The UDL namespace as in the UDL file. Defaults to the library crate name.
        namespace = "my_crate"
        // The Rust target of the build to use to generate the bindings. If unspecified, one of the available builds
        // will be automatically selected.
        build = RustAndroidTarget.Arm64
        // The variant of the build that makes the library to use. If unspecified, the UniFFI plugin automatically picks
        // one.
        variant = Variant.Debug
    }
}

If you want to generate bindings from a UDL file as well, you can specify the path using the generateFromUdl {} block.

uniffi {
    generateFromUdl {
        namespace = "..."
        build = ...
        variant = Variant.Debug
        // The UDL file. Defaults to "${crateDirectory}/src/${crateName}.udl".
        udlFile = layout.projectDirectory.file("rust/src/my_crate.udl")
    }
}

If you want to run ktlint on the generated bindings set formatCode to true.

uniffi {
    formatCode = true
}

When you use Kotlin targets not supported by the UniFFI plugin like js(), wasmJs(), or wasmWasi(), the UniFFI plugin generates stubs. This ensures that the Kotlin code is compiled successfully for all platforms. However, all generated functions except for RustObject(NoPointer) constructors will throw kotlin.NotImplementedError. We are trying to support as many platforms as possible. If you need to target WASM/JS, please use these stubs until WASM/JS support is released.