method safeEvery

Source

static Disposable safeEvery(interval, action()) {
  Duration duration;

  if (interval is Duration) {
    duration = interval;
  } else if (interval is int) {
    duration = new Duration(milliseconds: interval);
  } else if (interval is Interval) {
    duration = interval.duration;
  } else {
    throw new Exception("Invalid Interval: ${interval}");
  }

  ExecutableFunction schedule;
  Timer timer;
  bool disposed = false;
  schedule = () async {
    await action();
    if (!disposed) {
      new Timer(duration, schedule);
    }
  };

  timer = new Timer(duration, schedule);

  return new FunctionDisposable(() {
    if (timer != null) {
      timer.cancel();
    }
    disposed = true;
  });
}