Configuration

The generated Kotlin modules can be configured using a uniffi.toml configuration file.

Available options

Configuration name	Default	Description
package_name	uniffi	The Kotlin package name - ie, the value used in the package statement at the top of generated files.
cdylib_name	uniffi_{namespace}[^1]	The name of the compiled Rust library containing the FFI implementation (not needed when using generate --library).
generate_immutable_records	false	Whether to generate records with immutable fields (val instead of var).
custom_types		A map which controls how custom types are exposed to Kotlin. See the custom types section of the manual
external_packages		A map of packages to be used for the specified external crates. The key is the Rust crate name, the value is the Kotlin package which will be used referring to types in that crate. See the external types section of the manual
android	false	Used to toggle on Android specific optimizations
android_cleaner	android	Use the android.system.SystemCleaner instead of java.lang.ref.Cleaner. Fallback in both instances is the one shipped with JNA.
kotlin_target_version	"x.y.z"	When provided, it will enable features in the bindings supported for this version. The build process will fail if an invalid format is used.

Example

Custom types

# Assuming a Custom Type named URL using a String as the builtin.
[bindings.kotlin.custom_types.Url]
# Name of the type in the Kotlin code
type_name = "URL"
# Classes that need to be imported
imports = [ "java.net.URI", "java.net.URL" ]
# Functions to convert between strings and URLs
into_custom = "URI({}).toURL()"
from_custom = "{}.toString()"

External types

[bindings.kotlin.external_packages]
# This specifies that external types from the crate `rust-crate-name` will be referred by by the package `"kotlin.package.name`.
rust-crate-name = "kotlin.package.name"