为什么我的多对多关系字段未定义？

Question

我正在尝试创建一个关注者/关注系统，当我尝试将新用户附加到以下列表时，出现错误Cannot read property 'push' of undefined。这最终会创建 2 个单独的表，一张用于关注其他用户的用户，一张用于被其他用户关注的用户。不知道为什么它没有占据这个领域？任何帮助表示赞赏。

import { Length } from "class-validator";
import {
    Column,
    CreateDateColumn,
    Entity,
    JoinTable,
    ManyToMany,
    OneToMany,
    PrimaryColumn,
    RelationCount,
    Unique,
    UpdateDateColumn
} from "typeorm";

export class User {

    @PrimaryColumn()
    public user_id: string;

    @Column()
    public first_name: string;

    @Column()
    public last_name: string;

    @Column()
    public email: string;

    @Column()
    public phone_number: string;

    @Column()
    public username: string;

    @Column()
    @CreateDateColumn()
    public created_on: Date;

    @Column()
    @UpdateDateColumn()
    public updated_at: Date;

    @ManyToMany((type) => User, (user) => user.following)
    @JoinTable()
    public followers: User[];

    @ManyToMany((type) => User, (user) => user.followers)
    @JoinTable()
    public following: User[];

    @RelationCount((user: User) => user.followers)
    public followers_count: number;

    @RelationCount((user: User) => user.following)
    public following_count: number;
}

const { user_id, 
        follow_user_id } = req.
const user_repo = getRepository(User);
const user = await user_repo.findOne({
    where: {user_id}
});
const follow_user = new User();

follow_user.user_id = follow_user_id;
user.following.push(follow_user);
const result = user_repo.save(user);

错误指的是这一行user.following.push(follow_user);

UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'push' of undefined

Answer 1

我在 OneToMany 和 ManyToOne 关系中遇到了类似的错误，其中相对返回 null/未定义。

我使用的解决方法是将其放入 User 类中：

  @AfterLoad()
  async nullChecks() {
    if (!this.followers) {
      this.followers = []
    }

    if (!this.following) {
      this.following = []
    }
  }

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