用同一实例续集多对多关系答案

【问题标题】：Sequelize many to many relationship with same instance用同一实例续集多对多关系
【发布时间】：2020-07-10 07:17:40
【问题描述】：

我有用户，我想实现添加朋友。所以这会创建多对多关系，当使用相同的实例时，我如何使用 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

【问题讨论】：

标签： javascript node.js postgresql orm sequelize.js

【解决方案1】：

下面的例子使用"sequelize": "^5.21.3":

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();
  }
})();

它将创建表user_friends 存储对象的ID。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)

您可以拨打userInstance.getFriends()获取一些用户的朋友。

【讨论】：