如何在Sembast记录中侦听映射中的单个值？

var store = intMapStoreFactory.store('your_store_name');

import 'dart:async';

StreamTransformer<T, S> listenToValue<T, S>(
    S key, S Function(T) valueSelector) {
  return StreamTransformer.fromHandlers(
    handleData: (T data, EventSink<S> sink) {
      sink.add(valueSelector(data));
    },
    handleDone: (EventSink<S> sink) {
      // Cleanup code, if needed
    },
  );
}

Stream<S> listenToMapValue<S>(
    Database db, S key, S Function(Map<String, dynamic>) valueSelector) {
  var store = intMapStoreFactory.store('your_store_name');
  return store.record(key).onSnapshot(db).transform(
        listenToValue<S, S>(key, valueSelector),
      );
}

var db = await factory.openDatabase('your_database_path');
listenToMapValue<String>(db, 'your_key', (map) => map['your_value'])
  .listen((value) {
    // 处理监听到的值的变化
  });