javascript - 使用同一实例建立多对多关系

Question

我有用户，我想实现添加 friend 。
因此，这会创建多对多关系，如何在使用相同实例时使用 sequelize 创建多对多关系？

User.belongsToMany(User, {as: "friends", through: "friends})

但我不知道如何处理外键以及它们将被称为什么

Answer 1

下面使用 "sequelize": "^5.21.3" 的示例:

import { sequelize } from '../../db';
import { Model, DataTypes, BelongsToManyAddAssociationMixin } from 'sequelize';

class User extends Model {
  public getFriends!: BelongsToManyAddAssociationMixin<User, string>;
}
User.init(
  {
    name: DataTypes.STRING,
  },
  { sequelize, modelName: 'users' },
);

User.belongsToMany(User, { as: 'friends', through: 'user_friends' });

(async function test() {
  try {
    await sequelize.sync({ force: true });
    // seed
    const friendsOfUser1 = [{ name: 'james' }, { name: 'elsa' }];
    const friendsOfUser2 = [{ name: 'jane' }, { name: 'mike' }];
    await User.bulkCreate(
      [
        { name: 'jeremy', friends: friendsOfUser1 },
        { name: 'lynne', friends: friendsOfUser2 },
      ],
      { include: [{ model: User, as: 'friends' }] },
    );
    const jeremy = await User.findOne({ where: { name: 'jeremy' } });
    const firendsOfJeremy = await jeremy.getFriends();
    console.log(firendsOfJeremy);
  } catch (error) {
    console.log(error);
  } finally {
    await sequelize.close();
  }
})();

它将创建存储对象 ID 的表 user_friends。查看数据库中的数据记录:

node-sequelize-examples=# select * from user_friends;
 userId | friendId
--------+----------
      1 |        3
      1 |        4
      2 |        5
      2 |        6
(4 rows)

node-sequelize-examples=# select * from users;
 id |  name
----+--------
  1 | jeremy
  2 | lynne
  3 | james
  4 | elsa
  5 | jane
  6 | mike
(6 rows)

您可以调用 userInstance.getFriends() 来获取一些用户的 friend 。