Sample ffi project for iOS

The following commands

cargo build --target aarch64-apple-ios-sim
cargo build --release --target aarch64-apple-ios-sim

will build the static libraries for the iOS arm64 arch (simulation).

If you want you can also create static libs for the aarch64-apple-ios or x86_64-apple-ios targets.

Those static libraries *a. should be added as static libraries in the Build Phase for the Xcode project. Here only one is necessary, as only the name is important (which is the same for all configurations).

The paths have to be added to the Library Search Path in the Xcode Build Settings. At best use different paths for the different architectures in configs (arm64/arm64-sim/x86_64 and Debug/Release), so the correct static lib *.a are fetched.

But as mentioned - the static library has only been added once - for the name. The correct one is fetched via the Library Search Paths.

Also bridging headers are needed, so it can be used in Xcode. Therefore, add a Objective-C Bridging Header. Create a simple header with the same C signature like the #[no_mangle] annotated functions.

A bridging header can be dead simple as this one:

#ifndef FfiBridge_h
#define FfiBridge_h

int fetch_google();

#endif /* FfiBridge_h */

which has the same signature as the exported function in Rust in the lib.rs file.

#[no_mangle]
pub extern "C" fetch_google() -> i32 {
   //... fetch https://google.com and return the len() of the string
}

Inside the hello world iOS Swift project, you can just call the function like so:

import SwiftUI

struct ContentView: View {
    var body: some View {
        VStack {
            Image(systemName: "globe")
                .imageScale(.large)
                .foregroundColor(.accentColor)
            Text("Hello, Rust \(fetch_google())")
        }
        .padding()
    }
}