WIP: Swiftgen prototype and example

[liamappelbe]

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This is a prototype of swiftgen, and an example program that uses the Swift AVAudioPlayer API to play some audio from Dart.

example/generate_code.dart uses swiftgen to generate Dart bindings like this:

await generate(Config(
  target: Target(
    triple: 'x86_64-apple-macosx14.0',
    sdk: Uri.directory(
        '/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk'),
  ),
  input: SwiftModuleInput(module: 'AVFAudio'),
  tempDir: Uri.directory('temp'),
  outputModule: 'AVFAudioWrapper',
  objcSwiftFile: Uri.file('avf_audio_wrapper.swift'),
  ffigen: FfiGenConfig(
    output: Uri.file('avf_audio_bindings.dart'),
    outputObjC: Uri.file('avf_audio_wrapper.m'),
    externalVersions: ffigen.ExternalVersions(
      ios: ffigen.Versions(min: Version(12, 0, 0)),
      macos: ffigen.Versions(min: Version(10, 14, 0)),
    ),
    objcInterfaces: ffigen.DeclarationFilters(
      shouldInclude: (decl) => decl.originalName == 'AVAudioPlayerWrapper',
    ),
  ),
));

Then example/play_audio.dart uses the generated Dart bindings to play audio:

for (final file in args) {
  final fileStr = NSString(file);
  print('Loading $fileStr');
  final fileUrl = NSURL.fileURLWithPath_(fileStr);
  final player = AVAudioPlayerWrapper.alloc()
      .initWithContentsOf_error_(fileUrl, nullptr);
  if (player == null) {
    print('Failed to load audio');
    continue;
  }
  final durationSeconds = player.duration.ceil();
  print('$durationSeconds sec');
  final status = player.play();
  if (status) {
    print('Playing...');
    await Future<void>.delayed(Duration(seconds: durationSeconds));
  } else {
    print('Failed to play audio.');
  }
}

There are a few remaining hacks to iron out, due to https://github.com/dart-lang/native/issues/1775 and https://github.com/dart-lang/native/issues/1774.

[github-actions[bot]]

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// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

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[orestesgaolin]

Hey there, would you be able to briefly explain how could I run this locally? Should I execute example/generate_code.dart?

[liamappelbe]

@orestesgaolin Yeah, if you want to try the example you can run example/generate_code.dart to regenerate the bindings (avf_audio_bindings.dart etc) and example/play_audio.dart foo.mp3 to run the example.

[dcharkes]

Given we have a merged https://github.com/dart-lang/native/tree/main/pkgs/swiftgen, I presume this can be closed.

[orestesgaolin]

I don't see swiftgen updated on main... Is that something that needs to be synchronized with google's repos?

[dcharkes]

Oh, it's an empty directory, my bad! (I was in overzealous spring-cleaning-mode!)

[coveralls]

coverage: 83.521%. remained the same when pulling 7f979f0e6362db51bf7ed005527a7b23ab0f81b9 on swiftgen2 into d7ab0d55e01c0eb3c35c5af9fefd84c53ef55215 on main.

[liamappelbe]

https://github.com/dart-lang/native/pull/2585