| // 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<bool> isEmpty |
| /// Whether this stream contains any elements. |
| /// Waits for the first element of this stream, then completes the returned |
| /// future with `true`. |
| /// If the stream ends without emitting any elements, the returned future is |
| /// completed with `false`. |
| /// @description Checks that only first element of the stream is examined |
| /// @author a.semenov@unipro.ru |
| |
| library isEmpty_A02_t01; |
| import "dart:async"; |
| import "../../../Utils/expect.dart"; |
| |
| void check(Stream s, bool expected) { |
| int count = 0; |
| asyncStart(); |
| s = s.map( |
| (e) { |
| count++; |
| return e; |
| } |
| ); |
| s.isEmpty.then( |
| (bool actual) { |
| Expect.equals(expected ? 0 : 1, count); |
| Expect.equals(expected, actual); |
| asyncEnd(); |
| } |
| ); |
| } |
| |
| test(CreateStreamFunction create) { |
| check(create([]), true); |
| check(create([1, 2, 3, null]), false); |
| check(create(new Iterable.generate(0, (int index) => 1)), true); |
| check(create(new Iterable.generate(10, (int index) => 1)), false); |
| } |