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

```toml

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.

``rust // Use theswift_bridge::bridgemacro 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.

```sh 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\ | RustVec\ | | | SwiftArray\ | Array\ | Not yet implemented | | &[T] | | Not yet implemented | | &mut [T] | | Not yet implemented | | Box | | Not yet implemented | | Box D> | (A, B, C) -> D | Passing from Rust to Swift is supported, but Swift to Rust is not yet implemented. | | Box D> | (A, B, C) -> D | Not yet implemented | | [T; N] | | Not yet implemented | | *const T | UnsafePointer\ | | | *mut T | UnsafeMutablePointer\ | | | Option\ | Optional\ | | | Result\ | RustResult\ | | | 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.

```sh

Clone the repository

git clone git@github.com:chinedufn/swift-bridge.git cd swift-bridge

Run tests

cargo test --all && ./test-integration.sh ```

Contributing

If you're interesting in contributing to swift-bridge, check out the contributor's guide.

After getting familiar with the contribution process, try looking at some of the good first issues to see if any peak your interest.

These issues come with step-by-step instructions that should help guide you towards implementing your first patch.

Acknowledgements

• cxx inspired the idea of using a bridge module to describe the FFI boundary.

License

Licensed under MIT or Apache-2.0.