| // Copyright (c) 2011, 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. |
| |
| /** |
| * @assertion Future<T> firstWhere ( |
| * bool test(T element), {@deprecated dynamic defaultValue(), T orElse()}) |
| * |
| * Finds the first element of this stream matching test. |
| * |
| * Returns a future that is completed with the first element of this stream that |
| * test returns true for. |
| * |
| * If no such element is found before this stream is done, and a orElse function |
| * is provided, the result of calling orElse becomes the value of the future. If |
| * orElse throws, the returned future is completed with that error. |
| * |
| * If this stream emits an error before the first matching element, the returned |
| * future is completed with that error, and processing stops. |
| * |
| * Stops listening to the stream after the first matching element or error has |
| * been received. |
| * |
| * Internally the method cancels its subscription after the first element that |
| * matches the predicate. This means that single-subscription (non-broadcast) |
| * streams are closed and cannot be reused after a call to this method. |
| * |
| * If an error occurs, or if this stream ends without finding a match and with |
| * no orElse function provided, the returned future is completed with an error. |
| * |
| * The defaultValue parameter is deprecated, and orElse should be used instead. |
| * @description Checks that if element is found, it is passed to the resulting |
| * future. [orElse] is provided. |
| * @author kaigorodov |
| */ |
| library firstWhere_A01_t02; |
| |
| import "dart:async"; |
| import "../../../Utils/expect.dart"; |
| |
| void check(Stream<int?> s, bool test(int? element), Object? expected) { |
| asyncStart(); |
| bool orElseUsed = false; |
| Future f = s.firstWhere(test, orElse: () { |
| orElseUsed = true; |
| return 42; |
| }); |
| f.then((var actual) { |
| Expect.equals(expected, actual); |
| Expect.isFalse(orElseUsed); |
| asyncEnd(); |
| }); |
| } |
| |
| void test(CreateStreamFunction create) { |
| check(create([1, 2, 3]), (int? element) => true, 1); |
| check(create([1, 2, 3]), (int? element) => element != null, 1); |
| check(create([1, 2, 3, null]), (int? element) => element == null, null); |
| check(create([1, 2, 3]), (int? element) => element! > 2, 3); |
| check(create(new Iterable.generate(10, (int? index) => index! * 5)), |
| (int? element) => element != 30, 0); |
| check(create(new Iterable.generate(10, (int index) => index * 5)), |
| (int? element) => element == 30, 30); |
| } |