Executors in Dart for Flutter

executors.dart

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


void main(List<String> arguments) async {
	Executor executor = await Executor.create();
	executor.run(Task('Name 1', task1));
	executor.run(Task('Name 2', task2));
	executor.run(Task('Name 3', task3));
	print('sent');
	await Future.delayed(Duration(seconds: 4));
	executor.dispose();
	print('done');
}

Future<void> task1() async {
	print('hello');
	await Future.delayed(Duration(milliseconds: 500));
}

Future<void> task2() async {
	print('world');
	await Future.delayed(Duration(milliseconds: 500));
}

Future<void> task3() async {
	print('dart');
	await Future.delayed(Duration(milliseconds: 500));
}

typedef TaskHandler<TResult> = TResult Function();

class Task<TResult> {
	final String name;
	final TaskHandler<TResult> handler;

	const Task(this.name, this.handler);

	TResult call() {
		print('start   $this');
		final result = handler();
		print('end     $this');
		return result;
	}

	@override
	String toString() {
		return 'Task{$name}';
	}
}

class Executor {
	Isolate _isolate;
	SendPort _taskPort;
	SendPort _quitPort;

	Executor._();

	static Future<Executor> create() async {
		final executor = Executor._();
		final startupPort = ReceivePort();
		executor._isolate = await Isolate.spawn(_spawn, startupPort.sendPort);
		List<SendPort> ports = await startupPort.first;
		executor._taskPort = ports[0];
		executor._quitPort = ports[1];
		return executor;
	}

	void run<T>(Task<T> task) {
		_taskPort.send(task);
	}

	void dispose() {
		_quitPort.send(null);
		_isolate.kill();
	}

	static void _spawn(SendPort executorPort) {
		final ReceivePort taskPort = ReceivePort();
		final ReceivePort quitPort = ReceivePort();
		executorPort.send([taskPort.sendPort, quitPort.sendPort]);
		taskPort.listen((task) async {
			print('running $task');
			task();
		});
		quitPort.first.then((_) {
			quitPort.close();
			taskPort.close();
		});
	}
}