any<T> method

Future<T> any <T>(Iterable<Future<T>> futures)

Returns the result of the first future in futures to complete.

The returned future is completed with the result of the first future in futures to report that it is complete, whether it's with a value or an error. The results of all the other futures are discarded.

If futures is empty, or if none of its futures complete, the returned future never completes.

Implementation 

static Future<T> any<T>(Iterable<Future<T>> futures) {
  var completer = new Completer<T>.sync();
  var onValue = (T value) {
    if (!completer.isCompleted) completer.complete(value);
  };
  var onError = (error, stack) {
    if (!completer.isCompleted) completer.completeError(error, stack);
  };
  for (var future in futures) {
    future.then(onValue, onError: onError);
  }
  return completer.future;
}