Flutter对象关系映射插件flutter_orm的使用

flutter_orm 是一个基于注解的ORM库，灵感来源于Android的Room持久化库。它基于 sqflite，提供了更友好的API，并支持Android、iOS和MacOS。

主要特性

• 简单的API用于创建数据库和实体
• 支持CRUD操作
• 支持事务
• 支持自定义类型转换器
• 支持迁移
• 支持嵌入字段
• 支持外键

使用示例

1. 添加依赖

在你的Flutter项目中添加以下依赖：

dependencies:
  flutter_orm:
  sqflite:

dev_dependencies:
  flutter_orm_generator:
  build_runner:

2. 导入库

import 'package:flutter_orm/flutter_orm.dart';

注意：如果你对数据库结构（包括DB、Dao、Entity等）进行了任何更改，必须运行以下命令来应用更改：

flutter pub run build_runner build --delete-conflicting-outputs;

3. 定义实体（表）

使用 @Entity 注解来定义一个实体或表。你可以设置 tableName 和 indices 属性。如果没有指定 tableName，则默认使用类名作为表名。

@Entity(tableName: 'notes', indices: [
  Index(columns: ['text'], unique: true)
])
class Note {
  @PrimaryKey(autoGenerate: true)
  final int? id;

  final String text;
  final bool isEdited;
  final DateTime createDate;
  final DateTime? updateDate;

  @Column(name: 'lat')
  final double? latitude;

  @Column(name: 'lng')
  final double? longitude;

  @Ignore()
  final String? ignoreTest;

  @Column(name: 'defaultValueTest1', defaultValue: 'test')
  final String? defaultValueTest1;

  @Column(name: 'defaultValueTest2', defaultValue: '0')
  final int? defaultValueTest2;

  Note({
    this.id,
    required this.text,
    required this.isEdited,
    required this.createDate,
    this.updateDate,
    this.latitude,
    this.longitude,
    this.ignoreTest,
    this.defaultValueTest1,
    this.defaultValueTest2,
  });
}

4. 定义数据库

使用 @DB 注解定义数据库，并指定版本号和实体列表。

@DB(
  name: 'note_db',
  version: 1,
  entities: [Note],
)
abstract class NoteDB {
  @OnUpgrade()
  Future<void> onUpgrade(Database db, int oldVersion, int newVersion) async {
    print('onUpgrade');
  }

  @OnDowngrade()
  Future<void> onDowngrade(Database db, int oldVersion, int newVersion) async {
    print('onDowngrade');
  }

  @OnConfigure()
  Future<void> onConfigure(Database db) async {
    db.execute('PRAGMA foreign_keys = ON;');
  }

  @OnOpen()
  Future<void> onOpen(Database db) async {
    print('onOpen');
  }
}

5. 数据访问对象（DAO）

使用 @Dao 注解定义数据访问对象（DAO），并在其中定义方法来访问和操作数据。

@Dao()
abstract class NoteDao {
  @Insert(onConflict: OnConflictStrategy.ignore)
  Future<void> insert(Note note);

  @Query("select * from Note")
  Future<List<Note>> all();

  @Delete()
  Future<void> delete(Note note);
}

6. 数据库构建器

使用 @DBBuilder 注解定义一个抽象类，用于初始化数据库并生成访问数据库的方法。

@DBBuilder(databases: [NoteDB])
abstract class DatabaseBuilder {}

7. 初始化数据库

NoteDB noteDB = await DBContext.getNoteDB();
final dao = noteDB.noteDao();
int count = await dao.count() ?? 0;

8. 示例代码

以下是一个完整的示例，展示了如何使用 flutter_orm 插件来创建一个简单的笔记应用程序。

import 'package:flutter/material.dart';
import 'package:example/database_builder/database_builder.dart';
import 'package:example/db/note_db.dart';
import 'package:example/entities/note.dart';
import 'package:example/pages/notes_list_page.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'ORM Demo',
      theme: ThemeData(
        primarySwatch: Colors.red,
      ),
      home: const MyHomePage(title: 'ORM Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  [@override](/user/override)
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  late NoteDB noteDB;
  bool _initialized = false;

  [@override](/user/override)
  void initState() {
    super.initState();
    _initDB();
  }

  void _initDB() {
    DBContext.getNoteDB().then((db) {
      noteDB = db;
      _insertMockNote().then((_) {
        Future.delayed(const Duration(seconds: 3)).then((value) {
          setState(() {
            _initialized = true;
          });
        });
      });
    });
  }

  Future<void> _insertMockNote() async {
    int count = await noteDB.noteDao().count() ?? 0;
    if (count > 0) return;
    DateTime now = DateTime.now();
    await noteDB.noteDao().insert(Note(
          text: 'Mock Note 1',
          createDate: now,
          isEdited: false,
          userId: 1,
        ));
    await noteDB.noteDao().bulkInsert([
      Note(
        text: 'Mock Note 1',
        createDate: now,
        isEdited: false,
        userId: 1,
      ),
      Note(
        text: 'Mock Note 2',
        createDate: now,
        isEdited: false,
        userId: 1,
      ),
      Note(
        text: 'Mock Note 3(Embedded)',
        createDate: now,
        isEdited: false,
        address: Address(
          city: 'Tehran',
          street: 'Saei',
          addressName: AddressName(
            name: 'Work',
            flag: true,
          ),
        ),
        userId: 1,
      ),
    ]);
    print('mock notes inserted');
    await noteDB.noteDao().bulkUpdate([
      Note(
        id: 1,
        text: 'Mock Note 1 edited',
        latitude: 1.1,
        createDate: now,
        updateDate: DateTime.now(),
        isEdited: true,
        userId: 1,
      ),
      Note(
        id: 2,
        text: 'Mock Note 2 edited',
        latitude: 1.2,
        createDate: now,
        updateDate: DateTime.now(),
        isEdited: true,
        userId: 1,
      ),
    ]);
    print('mock notes updated');
  }

  [@override](/user/override)
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text(widget.title)),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              _initialized ? 'NoteDB initialized' : 'Initializing NoteDB...',
              style: const TextStyle(fontSize: 20),
            ),
            if (_initialized)
              MaterialButton(
                child: const Text('Go To Notes App'),
                color: Colors.green,
                textColor: Colors.white,
                onPressed: () {
                  Navigator.of(context).push(MaterialPageRoute(
                    builder: (context) => NotesListPage(noteDB),
                  ));
                },
              ),
          ],
        ),
      ),
    );
  }
}