Flutter:如何在创建类时最好地实例化SQFlite db对象

import 'package:sqflite/sqflite.dart';
import 'dart:async';

class DatabaseHelper {
  static final DatabaseHelper _instance = DatabaseHelper._internal();
  factory DatabaseHelper() => _instance;
  static Database? _database;

  Future<Database> get database async {
    if (_database != null) return _database!;
    _database = await _initDatabase();
    return _database!;
  }

  DatabaseHelper._internal();

  Future<Database> _initDatabase() async {
    return openDatabase(
      'my_database.db',
      version: 1,
      onCreate: _onCreate,
    );
  }

  void _onCreate(Database db, int version) async {
    await db.execute('''
      CREATE TABLE users (
        id INTEGER PRIMARY KEY,
        name TEXT NOT NULL
      )
    ''');
  }
}

class UserRepository {
  final Database? _database;

  UserRepository(this._database);

  Future<void> addUser(String name) async {
    final db = await _database!;
    await db.insert(
      'users',
      {'name': name},
    );
  }
}