swift-bridge

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.

Installation

# In your Cargo.toml

[build-dependencies]
swift-bridge-build = "0.1"

[dependencies]
swift-bridge = "0.1"

Book

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.
#[swift_bridge::bridge]
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 {
        ById(UserId),
        ByName(String),
    }

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

        #[swift_bridge(init)]
        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;

        #[swift_bridge(Copy(4))]
        type UserId;

        #[swift_bridge(init)]
        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]);
    }
}

#[derive(Copy)]
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.

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

License

Licensed under MIT or Apache-2.0.

lib.rs:

The swift-bridge CLI.