LibTest/async/StreamTransformer/StreamTransformer.fromHandlers_A01_t02.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.

// @dart = 2.9

/// @assertion factory StreamTransformer.fromHandlers({void handleData(S data,
///   EventSink<T> sink), void handleError(Object error, StackTrace stackTrace,
///   EventSink<T> sink), void handleDone(EventSink<T> sink)})
/// Creates a StreamTransformer that delegates events to the given functions.
///
/// @description Checks that handleData() is called on data events and
/// transformed stream gets data that are written to sink.
/// handleError is not provided, so error events are unchanged.
/// @author ilya

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

main() {
  Stream<int> s = new Stream.fromIterable([1,2,3,4,5]);
  
  // odd numbers as data events, even numbers as error events
  s = s.map((x) => x.isOdd ? x : throw x);

  StreamTransformer<int, dynamic> tr = new StreamTransformer.fromHandlers(
    handleData: (x, sink) {
      sink.add(x+10);
    }
  );
  
  int data = 11;
  int error = 2;

  asyncStart();
  s.transform(tr).listen(
    (x) {
      Expect.equals(data, x);
      data += 2;
    },
    onError:(x) {
      Expect.equals(error, x);
      error += 2;
    },
    onDone:() {
      asyncEnd();
    }
  );
}