Flutter对象关系映射插件jaguar_orm的使用

jaguar_orm

来源生成的ORM，支持关系（一对一、一对多、多对多）、预加载、级联、多态关系等。

特性

• 关系
  • 一对一
  • 一对多
  • 多对多
• 预加载
• 级联
  • 级联插入
  • 级联更新
  • 级联删除
• 迁移
• 多态关系
• 复合主键
• 复合外键

开始使用

声明模型

class User {
  [@PrimaryKey](/user/PrimaryKey)()
  String id;

  String name;

  static const String tableName = '_user';

  String toString() => "User($id, $name)";
}

声明Bean

Bean为模型执行数据库操作。例如，UserBean为User模型执行操作。Bean的大部分功能将通过源代码生成。

[@GenBean](/user/GenBean)()
class UserBean extends Bean<User> with _UserBean {
  UserBean(Adapter adapter) : super(adapter);
}

生成Bean逻辑

jaguar_orm 使用 source_gen 和 jaguar_orm_gen 来从Bean规范生成Bean逻辑。

在 dev_dependencies 中添加以下依赖：

build_runner:
jaguar_orm_gen:

运行以下命令以生成Bean逻辑：

pub run build_runner build

连接到数据库

我们将使用PostgreSQL进行此教程。PgAdapter 在包 jaguar_query_postgres 中找到。

final PgAdapter _adapter = 
    new PgAdapter('example', username: 'postgres', password: 'dart_jaguar');
await _adapter.connect();

创建Bean实例

Bean内部使用 jaguar_query 的 Adapter 接口与数据库通信。让我们创建一个 UserBean 实例。

final userBean = new UserBean(_adapter);

删除表

await userBean.drop();

创建表

await userBean.createTable();

插入新记录

await userBean.insert(new User()
    ..id = '1'
    ..name = 'teja');

按主键获取记录

User user = await userBean.find('1');

获取所有记录

List<User> users = await userBean.getAll();

更新记录

User user = await userBean.find('1');
user.name = 'teja hackborn';
await userBean.update(user);

按ID删除

await userBean.remove('1');

删除所有记录

await userBean.removeAll();

示例

一对一示例

class User {
  [@PrimaryKey](/user/PrimaryKey)()
  String id;

  String name;

  [@HasOne](/user/HasOne)(AddressBean)
  Address address;

  static const String tableName = '_user';

  String toString() => "User($id, $name, $address)";
}

class Address {
  [@PrimaryKey](/user/PrimaryKey)()
  String id;

  [@BelongsTo](/user/BelongsTo)(UserBean)
  String userId;

  String street;

  static String tableName = 'address';

  String toString() => "Post($id, $userId, $street)";
}

[@GenBean](/user/GenBean)()
class UserBean extends Bean<User> with _UserBean {
  UserBean(Adapter adapter)
      : addressBean = new AddressBean(adapter),
        super(adapter);

  final AddressBean addressBean;

  Future createTable() {
    final st = Sql
        .create(tableName)
        .addStr('id', primary: true, length: 50)
        .addStr('name', length: 50);
    return execCreateTable(st);
  }
}

[@GenBean](/user/GenBean)()
class AddressBean extends Bean<Address> with _AddressBean {
  AddressBean(Adapter adapter) : super(adapter);

  Future createTable() {
    final st = Sql
        .create(tableName)
        .addStr('id', primary: true, length: 50)
        .addStr('street', length: 150)
        .addStr('user_id', length: 50, foreignTable: '_user', foreignCol: 'id');
    return execCreateTable(st);
  }
}

/// The adapter
PgAdapter _adapter =
    new PgAdapter('postgres://postgres:dart_jaguar@localhost/example');

main() async {
  // Connect to database
  await _adapter.connect();

  // Create beans
  final userBean = new UserBean(_adapter);
  final addressBean = new AddressBean(_adapter);

  // Drop old tables
  await addressBean.drop();
  await userBean.drop();

  // Create new tables
  await userBean.createTable();
  await addressBean.createTable();

  // Cascaded One-To-One insert
  {
    final user = new User()
      ..id = '1'
      ..name = 'Teja'
      ..address = (new Address()
        ..id = '1'
        ..street = 'Stockholm');
    await userBean.insert(user, cascade: true);
  }

  // Fetch One-To-One preloaded
  {
    final user = await userBean.find('1', preload: true);
    print(user);
  }

  // Manual One-To-One insert
  {
    User user = new User()
      ..id = '2'
      ..name = 'Kleak';
    await userBean.insert(user, cascade: true);

    user = await userBean.find('2');

    final address = new Address()
      ..id = '2'
      ..street = 'Stockholm';
    addressBean.associateUser(address, user);
    await addressBean.insert(address);
  }

  // Manual One-To-One preload
  {
    final user = await userBean.find('2');
    print(user);
    user.address = await addressBean.findByUser(user.id);
    print(user);
  }

  // Preload many
  {
    final users = await userBean.getAll();
    print(users);
    await userBean.preloadAll(users);
    print(users);
  }

  // Cascaded One-To-One update
  {
    User user = await userBean.find('1', preload: true);
    user.name = 'Teja Hackborn';
    user.address.street = 'Stockholm, Sweden';
    await userBean.update(user, cascade: true);
  }

  // Fetch One-To-One relationship preloaded
  {
    final user = await userBean.find('1', preload: true);
    print(user);
  }

  // Cascaded removal of One-To-One relation
  await userBean.remove('1', true);

  // Remove addresses belonging to a User
  await addressBean.removeByUser('2');

  exit(0);
}