swift-bridge

Call Rust from Swift and vice versa.

swift-bridge generates code that helps you call Swift from Rust and vice versa.

swift-bridge takes inspiration from the bridge module idea pioneered by cxx.

Current Status

swift-bridge is not yet production ready.

We need to use it more before we can be confident enough in the generated FFI glue to call swift-bridge production ready.

Right now I'm looking for feedback in order to continue to improve the APIs and the generated code.

I can especially use feedback from people with Swift experience, since I don't have much.

Installation

# In your Cargo.toml

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

[dependencies]
swift-bridge = "0.1"

Quick Peek

Here's a quick peek at how bindings look.

A more thorough walk through of swift-bridge can be found in the book (TODO: Link to GitHub pages).

// lib.rs

#[swift_bridge::bridge]
mod ffi {
    // Shared types 
    #[swift_bridge(swift_repr = "struct")]
	struct ASharedStruct {
	    field: u32
	}

    // Exposes super::ARustStack to Swift.
    extern "Rust" {
        type ARustStack;

        fn push (&mut self, val: u8);

        fn pop (&mut self) -> Option<u8>;
      
        fn as_slice (&self) -> &[u8];

        fn do_stuff(override: Option<u8>);
    }

    // Exposes a Swift class to Rust.
    extern "Swift" {
        type SwiftApiClient;

        #[swift_bridge(init)]
        fn new_with_timeout(timeout: u8) -> SwiftApiClient;

        #[swift_bridge(associated_to = FileSystemClient)]
        fn version () -> String;

        fn post_bytes(&self, bytes: &[u8]);
    }
}

TODO's before open sourcing

Create a tutorial on setting up a project

Built-In Types

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
&str	RustStr
Vec	RustVec<T>
SwiftArray<T>	Array<T>	Not yet implemented
&[T]	UnsafeBufferPointer<T>
&mut [T]	UnsafeMutableBufferPointer<T>	Not yet implemented
SwiftString	String
Box		Not yet implemented
[T; N]		Not yet implemented
*const T	UnsafePointer<T>
*mut T	UnsafeMutablePointer<T>
Option<T>	Optional<T>	Currently only supports function return types that are primitive (i.e. `-> Option<i32>`), or `-> Option<String>`.. More support will come. Other places such as function arguments are not yet implemented but will come.
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

swift-bridge 0.1.13