An init function for creating a Dart/Flutter Isolate. It returns the SendPort so the main thread can send messages to the Isolate. It also listens for messages passed from the Isolate.

isolate-initializer.dart

Future<SendPort> initIsolate() async {
  Completer completer = new Completer<SendPort>();
  ReceivePort isolateToMainStream = ReceivePort();

  isolateToMainStream.listen((data) {
    if (data is SendPort) {
      SendPort mainToIsolateStream = data;
      completer.complete(mainToIsolateStream);
    } else {
      print('[isolateToMainStream] $data');
    }
  });

  Isolate myIsolateInstance = await Isolate.spawn(myIsolate, isolateToMainStream.sendPort);
  return completer.future;
}