#swift #ffi #bindings #ios #mac

bin+lib swift-bridge-cli

Parse Rust files for swift-bridge modules and generate the corresponding Swift and C code for them

24 releases

0.1.51 Feb 28, 2023
0.1.48 Jan 29, 2023
0.1.44 Dec 15, 2022
0.1.41 Oct 28, 2022
0.1.29 Mar 12, 2022

#3 in #interop

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Rust 778 SLoC // 0.0% comments Swift 237 SLoC // 0.1% comments

swift-bridge Actions Status docs crates.io

swift-bridge facilitates Rust and Swift interop.

swift-bridge is a library that lets you pass and share high-level types such as Option<T>, String, Structs and Classes between Rust and Swift.

It also lets you bridge higher level language features between Rust and Swift, such as async functions and generics.


# In your Cargo.toml

swift-bridge-build = "0.1"

swift-bridge = "0.1"


You can find information about using Rust and Swift together in The swift-bridge Book.

Quick Peek

You use swift-bridge by declaring the types and functions that you want to import and export in a "bridge module", and then annotating that bridge module with the #[swift_bridge::bridge] macro.

Then, at build time, you use either the swift-bridge-build API or the swift-bridge-cli CLI to parse your annotated bridge modules and generate the Swift and C side of the FFI layer.

Here's a quick peek at how you might describe an FFI boundary between Swift and Rust using a bridge module.

// Use the `swift_bridge::bridge` macro to declare a bridge module that
// `swift-bridge-build` will parse at build time in order to generate
// the necessary Swift and C FFI glue code.
mod ffi {
    // Create shared structs where both Rust and Swift can directly access the fields.
    struct AppConfig {
        file_manager: CustomFileManager,

    // Shared enums are also supported
    enum UserLookup {

    // Export Rust types, functions and methods for Swift to use.
    extern "Rust" {
        type RustApp;

        fn new(config: AppConfig);
        fn insert_user(&mut self, user_id: UserId, user: User);
        fn get_user(&self, lookup: UserLookup) -> Option<&User>;

    extern "Rust" {
        type User;

        type UserId;

        fn new(user_id: UserId, name: String, email: Option<String>) -> User;

    // Import Swift classes and functions for Rust to use.
    extern "Swift" {
        type CustomFileManager;
        fn save_file(&self, name: &str, contents: &[u8]);

struct UserId(u32);

Quick Start

The swift-bridge repository contains example applications that you use to quickly try out the library, or as a starting point for your own Swift + Rust based application.

For example, here's how to run the codegen-visualizer example project locally.

git clone https://github.com/chinedufn/swift-bridge
cd swift-bridge/examples/codegen-visualizer

open CodegenVisualizer/CodegenVisualizer.xcodeproj
# *** Click the "Run" button at the top left of Xcode ***

You can find information about using Rust and Swift together in The swift-bridge Book.

Built-In Types

In addition to allowing you to share your own custom structs, enums and classes between Rust and Swift, swift-bridge comes with support for a number of Rust and Swift standard library types.

name in Rust name in Swift notes
u8, i8, u16, i16... etc UInt8, Int8, UInt16, Int16 ... etc
bool Bool
String, &String, &mut String RustString, RustStringRef, RustStringRefMut
&str RustStr
Vec<T> RustVec<T>
SwiftArray<T> Array<T> Not yet implemented
&[T] Not yet implemented
&mut [T] Not yet implemented
Box Not yet implemented
Box<dyn FnOnce(A,B,C) -> D> (A, B, C) -> D Passing from Rust to Swift is supported, but Swift to Rust is not yet implemented.
Box<dyn Fn(A,B,C) -> D> (A, B, C) -> D Not yet implemented
[T; N] Not yet implemented
*const T UnsafePointer<T>
*mut T UnsafeMutablePointer<T>
Option<T> Optional<T>
Result<T, E> RustResult<T, E>
Have a Rust standard library type in mind?
Open an issue!
Have a Swift standard library type in mind?
Open an issue!

To Test

To run the test suite.

# Clone the repository
git clone git@github.com:chinedufn/swift-bridge.git
cd swift-bridge

# Run tests
cargo test --all && ./test-integration.sh


Licensed under MIT or Apache-2.0.


The swift-bridge CLI.


~154K SLoC