#swift #ffi #bindings #ios #mac

swift-bridge-build

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

36 releases

Uses new Rust 2021

0.1.35 Jul 27, 2022
0.1.33 May 10, 2022
0.1.29 Mar 12, 2022
0.1.15 Dec 28, 2021
0.1.5 Nov 26, 2021

#29 in macOS and iOS APIs

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1,072 downloads per month
Used in 2 crates

Apache-2.0/MIT

590KB
15K SLoC

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.

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.

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
[T; N] Not yet implemented
*const T UnsafePointer<T>
*mut T UnsafeMutablePointer<T>
Option<T> Optional<T>
Result<T> Not yet implemented
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

License

Licensed under MIT or Apache-2.0.

Dependencies

~300–760KB
~17K SLoC