Flutter - SEMBAST 与 built_value 的集成，如何将模型插入 sembast db

Question

我尝试使用将 Post 对象插入 SEMBAST 数据库，但需要 toMap() 才能插入数据库 请在下面找到我的代码

import 'package:built_collection/built_collection.dart';
import 'package:built_value/built_value.dart';
import 'package:built_value/serializer.dart';

import '../serializers.dart';
import 'articles.dart';

part 'news.g.dart';

abstract class News implements Built<News, NewsBuilder> {
  News._();

  factory News([updates(NewsBuilder b)]) = _$News;

  @BuiltValueField(wireName: 'status')
  String get status;
  @BuiltValueField(wireName: 'totalResults')
  int get totalResults;
  @BuiltValueField(wireName: 'articles')
  BuiltList<Articles> get articles;
  String toJson() {
    return json.encode(serializers.serializeWith(News.serializer, this));
  }

  static News fromJson(String jsonString) {
    return serializers.deserializeWith(
        News.serializer, json.decode(jsonString));
  }

  static Serializer<News> get serializer => _$newsSerializer;


}

我的数据源文件是

import 'package:boilerplate/data/local/constants/db_constants.dart';
import 'package:boilerplate/models/news/news.dart';
import 'package:boilerplate/models/post/post.dart';
import 'package:boilerplate/models/post/post_list.dart';
import 'package:sembast/sembast.dart';

class NewsDataSource {
  // A Store with int keys and Map<String, dynamic> values.
  final _postsStore = intMapStoreFactory.store(DBConstants.STORE_NAME);

  // Private getter to shorten the amount of code needed to get the
  // singleton instance of an opened database.
//  Future<Database> get _db async => await AppDatabase.instance.database;

  // database instance
  final Future<Database> _db;

  // Constructor
  PostDataSource(this._db);


  // DB functions:--------------------------------------------------------------
  Future insert(News news) async {
    return await _postsStore.add(await _db, post);
  }


}

但插入语法 await _postsStore.add(await _db, post); 显示错误
Future<int> StoreRef.add(DatabaseClient client, Map<String, dynamic> value)

请帮我解决一下

Answer 1

如前所述，sembast 与 firestore 和 indexed_db 一样需要映射。您必须以兼容的方式使用 built_value 进行序列化。一种方法是在定义序列化程序时使用 StandardJsonPlugin：

@SerializersFor([News])
final Serializers serializers =
    (_$serializers.toBuilder()..addPlugin(StandardJsonPlugin())).build();

然后您可以从您的新闻对象生成地图：

var map = serializers.serializeWith(News.serializer, news);

您的插入方法将是这样的：

Future insert(News news) async {
  var map = serializers.serializeWith(News.serializer, news);
  return await _postsStore.add(await _db, map);
}