Bidirectional communication Isolates

isolate_service.dart

import 'dart:async';
import 'dart:isolate';

void main() async {
  await IsolateService.init();
  IsolateService?.updates?.listen((e) => print('message from the isolate: $e'));
  IsolateService.sendMessage('message from main');
}

class IsolateService {
  static ReceivePort _isolateToMain;
  static StreamController<Object> _controller;
  static SendPort _sendPort;
  static Future<void> init() async {
    _sendPort = await run();
    return;
  }

  static Future<SendPort> run() async {
    _isolateToMain ??= ReceivePort();
    final completer = Completer<SendPort>();
    _controller = StreamController<Object>();
    _isolateToMain.listen(
      (m) {
        if (m is SendPort) {
          completer.complete(m);
        } else {
          _controller.add(m);
        }
      },
    );
    await Isolate.spawn(_runner, _isolateToMain.sendPort);
    return completer.future;
  }

  static void sendMessage(Object message) => _sendPort?.send(message);

  static Stream<Object> get updates => _controller?.stream;

  static void _runner(SendPort isolateToMain) {
    final mainToIsolate = ReceivePort();
    isolateToMain.send(mainToIsolate.sendPort);
    mainToIsolate.listen((message) => print('[mainToIsolateStream] $message'));
    isolateToMain.send('This is from my isolate');
  }
}