LibTest/async/Stream/Stream.eventTransformed_A01_t01.dart

/*
 * 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 factory Stream.eventTransformed(Stream source,
 *   EventSink mapSink(EventSink<T> sink))
 * Creates a stream where all events of an existing stream are piped through
 * a sink-transformation.
 * The given mapSink closure is invoked when the returned stream is listened
 * to. All events from the source are added into the event sink that is
 * returned from the invocation. The transformation puts all transformed
 * events into the sink the mapSink closure received during its invocation.
 * Conceptually the mapSink creates a transformation pipe with the input sink
 * being the returned EventSink and the output sink being the sink it received.
 * @description Checks that data events are produced according to transform. 
 * @author ilya
 */

import "dart:async";
import "../../../Utils/async_utils.dart";
import "../../../Utils/expect.dart";

// transform: skip evens, produce number and its double
class MySink implements EventSink<int> {
  final _sink;
  MySink(this._sink);
  void add(int i) {
    if (i.isOdd) {
      _sink.add(i);
      _sink.add(i*2);
    }
  }
  void addError(e, [st]) => _sink.addError(e, st);
  void close() => _sink.close();
}

var input = [1,2,3,4,5];
var expected = [1,2,3,6,5,10];

main() {
  var s = new Stream.fromIterable(input);
  var s2 = new Stream.eventTransformed(s, (sink) => new MySink(sink));

  asyncStart();
  s2.toList().then((x) {
    Expect.listEquals(expected, x);
    asyncEnd();
  });
}