您如何在DART（Bloc/Flutter）中以有效的方式进行此列表操作？

Question

我有以下状态包含2个单词的bloc，

// 2 words are fixed and same length.
// in word_state.dart
abstract class WordState extends Equatable 
  const WordState(this.quest, this.answer, this.word, this.clicked);
  final List<String> wordA; // WordA = ['B','A','L',L']
  final List<String> wordB; // WordB = ['','','','']
  @override
  List<Object> get props => [wordA,wordB];
}

我想添加和删除字母。

// in word_event.dart
class AddLetter extends WordEvent {
  final int index;
  const AddLetter(this.index);
}
class RemoveLetter extends WordEvent {
  final int index;
  const RemoveLetter(this.index);
}

1.Add： 如果我在Worda中选择“ L”的索引，则在WordB中首次出现“（空）的第一次出现”中添加字母“ L”。

// in word_bloc.dart 
void _onLetterAdded(AddLetter event, Emitter<WordState> emit) {
  final b = [...state.wordB]; 
  b[b.indexOf('')] = state.wordA[event.index];
  emit(WordLoaded(state.wordA, b));
}
//wordB, ['','','',''] into ['L','','','']

2.示威： 如果我取消了Worda中“ L”索引的选择，那么我删除WordB中字母“ L”的最后一个事件，然后将右侧字母转移到左侧

 void _onLetterRemoved(RemoveLetter event, Emitter<WordState> emit) {
    final b = [...state.wordB];
    final index = b.lastIndexOf(state.wordA[event.index]);
    for (int i = index; i < 4 - 1; i++) { 
      b[i] = b[i + 1];
    }
    b[3] = '';
    emit(WordLoaded(state.wordA, b));
  }
}
// What i am trying to
// ['B','L','A','L']
// if index is 1 then ['B','A','L','']

，但我想有效地进行列表操作。

Answer 1

您可以检查此代码理解并在Dart Pad上运行它。

  List<String> wordA=['B','A','L','L'];
  List<String> wordB=['','','',''];

  List<String> wordBAll=['B','L','A','L'];
  void main() {
  wordB.insert(0,wordA[2]);
  wordBAll.removeAt(wordBAll.length-1);
  print(wordB);
  print(wordBAll);

}