# swift-bridge [](https://github.com/chinedufn/swift-bridge/actions) [](https://docs.rs/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 awesome bridge module macro based approach pioneered by [cxx](https://github.com/dtolnay/cxx)._
## Installation
```toml
# In your Cargo.toml
[build-dependencies]
swift-bridge-build = "0.1"
[dependencies]
swift-bridge = "0.1"
```
## Phases
- Put the library out to get feedback from bleeding edge users.
- Continue to support more standard library types.
- Continue to hone the API based on real usage feedback.
- Figure out the safety story. What should be marked as safe vs. unsafe?
- Focus on making usage of swift-bridge feel ergonomic.
- Polish the documentation, examples and tutorials
- Get to a point where we feel that there has been enough, real world production use
and feedback for us to be confident that the user-facing API's won't need any breaking
changes.
- Release swift-bridge version 1.0
## Quick Peek
TODO: Shorten this quick peak.. we don't need to include the build script, for example
---
Here's a quick peek at the Rust and Swift of a bridge that should give you a sense of how bindings look.
A more thorough walk through of `swift-bridge` can be found in the book (TODO: Link to GitHub pages).
```rust
// build.rs
fn main() {
let bridges = vec!["src/lib.rs"];
let out_dir = "./generated";
swift_bridge_build::parse_bridges(&bridges)
.write_all_concatenated(out_dir);
for path in &bridges {
println!("cargo:rerun-if-changed={}", path);
}
}
```
```rust
// lib.rs
#[swift_bridge::bridge]
mod ffi {
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>);
}
extern "Swift" {
type SwiftApiClient;
#[swift_bridge(init)]
fn new_with_timeout(timeout: u8) -> SwiftApiClient;
#[swift_bridge(associated_to = FileSystemClient)]
fn version () -> u32;
fn set_timeout(&self, timeout: u8);
}
}
struct ARustStack(Vec<u8>);
impl ARustStack {
fn push(&mut self, val: u8) {
self.0.push(val);
}
fn pop(&mut self) -> Option<u8> {
self.0.pop();
}
fn as_slice(&self) -> &[u8] {
self.0.pop();
}
}
fn do_stuff(override: Option<u8>) {
assert_eq!(SwiftApiClient::version(), 1);
let client = SwiftApiClient::new_with_timeout(10);
if let Some(override) = override {
client.setTimeout(20)
}
}
```
```swift
// Swift
class SwiftApiClient {
var timeout: UInt8
init(timeout: UInt8) {
self.timeout = timeout
}
class func version() -> u32 {
1
}
func setTimeout(timeout: UInt8) {
self.timeout = timeout
}
}
```
## TODO's before open sourcing
We don't need to solve all of these, but we should at least create issues
- Look up how to programatically set the linking settings and programatically set the run script.
Our docs can recommend that as well as show how to manually set them
- Remove `#[no_mangle]` since we're using link_name and export_name
## Quick Peek
- Write instructions on going from 0 to most basic iOS app
- Add book chapter on setting up iOS app from scratch
- Create examples dir example of iOS app
- Create examples dir example of macOS app
## 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<T> | RustVec\<T> | |
| SwiftArray\<T> | Array\<T> | Not yet implemented |
| &[T] | UnsafeBufferPointer\<T> | |
| &mut [T] | UnsafeMutableBufferPointer\<T> | Not yet implemented |
| SwiftString | String | |
| Box<T> | | Not yet implemented |
| [T; N] | | Not yet implemented |
| *const T | UnsafePointer\<T> | |
| *mut T | UnsafeMutablePointer\<T> | |
| Option\<T> | Optional\<T> | Currently only supported for primitive function return types.<br /> Other places such as function arguments are not yet implemented.<br /> Non primitive T is not yet implemented. |
| Result\<T> | | Not yet implemented |
| Have a Rust standard library type in mind?<br /> Open an issue! | | |
| | Have a Swift standard library type in mind?<br /> 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
```
## See Also
- [Rust on iOS](https://mozilla.github.io/firefox-browser-architecture/experiments/2017-09-06-rust-on-ios.html)
- A blog post by Mozilla that explains how to run Rust on iOS.