| // Copyright (c) 2015, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| library which.src.util; |
| |
| import 'dart:async'; |
| |
| /// Transparently call `firstWhere` on a [Stream] or [Iterable]. |
| // TODO: Remove once https://dartbug.com/22028 is fixed. |
| firstWhere(sequence, test, { orElse() }) => sequence is Iterable ? |
| sequence.firstWhere(test, orElse: orElse) : |
| _streamFirstWhere(sequence, test, orElse: orElse); |
| |
| Future _streamFirstWhere(Stream stream, test(item), { orElse() }) { |
| var pairs = stream.asyncMap((item) => test(item).then((result) => [item, result])); |
| return pairs.firstWhere((pair) => pair.last, defaultValue: () => [orElse(), null]).then((pair) => pair.first); |
| } |
| |
| /// The identity function simply returns its argument ([x]). |
| identity(x) => x; |