BLoK example

main.dart

// forked from https://qiita.com/kabochapo/items/8738223894fb74f952d3

import 'dart:async';

void main() {
  final data = {'イチゴ': '苺', 'イチジク': '無花果', 'リンゴ': '林檎'};

  final controller = StreamController<String>();

  controller.sink.add('イチゴ');
  controller.sink.add('ドラゴンフルーツ');
  controller.sink.add('イチジク');
  controller.sink.add('リンゴ');
  controller.sink.add('オレンジ');

  final toKanji = StreamTransformer<String, String>.fromHandlers(
    handleData: (value, sink) {
      if (data.containsKey(value) && (data[value] != null)) {
        sink.add(data[value]!);
      } else {
        sink.addError('$value の漢字は不明です');
      }
    }
  );

  controller.stream
    .transform(toKanji)
    .listen(
      (value) { print(value); },
      onError: (err) { print('[エラー] $err'); }
    );
}