is there any way to cancel a dart Future?

Question

In a Dart UI, I have a button [submit] to launch a long async request. The [submit] handler returns a Future. Next, the button [submit] is replaced by a button [cancel] to a

Answer 1

my 2 cents worth...

class CancelableFuture {
  bool cancelled = false;
  CancelableFuture(Duration duration, void Function() callback) {
    Future<void>.delayed(duration, () {
      if (!cancelled) {
        callback();
      }
    });
  }

  void cancel() {
    cancelled = true;
  }
}

Answer 2

How to cancel Future.delayed

A simple way is to use Timer instead :)

Timer _timer;

void _schedule() {
  _timer = Timer(Duration(seconds: 2), () { 
    print('Do something after delay');
  });
}

@override
void dispose() {
  super.dispose();
  _timer?.cancel();
}

Answer 3

One way I accomplished to 'cancel' a scheduled execution was using a Timer. In this case I was actually postponing it. :)

Timer _runJustOnceAtTheEnd;

void runMultipleTimes() {
  _runJustOnceAtTheEnd?.cancel();
  _runJustOnceAtTheEnd = null;

  // do your processing

  _runJustOnceAtTheEnd = Timer(Duration(seconds: 1), onceAtTheEndOfTheBatch);
}

void onceAtTheEndOfTheBatch() {
  print("just once at the end of a batch!");
}


runMultipleTimes();
runMultipleTimes();
runMultipleTimes();
runMultipleTimes();

// will print 'just once at the end of a batch' one second after last execution

The runMultipleTimes() method will be called multiple times in sequence, but only after 1 second of a batch the onceAtTheEndOfTheBatch will be executed.