ManyToOne / OneToMany - typeORM - postgresSQL

Question

所以，我对 typeORM 和 postgres DB 有点陌生，我发现有些东西让我有点困惑，但是，在告诉您我的问题之前，让我向您展示一些代码

所以，这是一个名为 Vote 的实体

import {
  Entity as TOEntity,
  Column,
  JoinColumn,
  Index,
  BeforeInsert,
  ManyToOne
} from "typeorm";

import Entity from "./Entity";
import User from "./User";
import Post from "./Post";
import Comment from "./Comment";

@TOEntity("votes")
export default class Vote extends Entity {
  constructor(vote: Partial<Vote>) {
    super();
    Object.assign(this, vote);
  }

  @Column()
  value: number;

  @ManyToOne(() => User)
  @JoinColumn({ name: "username", referencedColumnName: "username" })
  user: User;

  @Column()
  username: string;

  @ManyToOne(() => Post)
  post: Post;

  @ManyToOne(() => Comment)
  comment: Comment;
}

这个叫做评论

import {
  Entity as TOEntity,
  Column,
  ManyToOne,
  OneToMany,
  JoinColumn,
  BeforeInsert,
  Index
} from "typeorm";

import Entity from "./Entity";
import User from "./User";
import Post from "./Post";
import Vote from "./Vote";
import { makeid } from "../util/helpers";

@TOEntity("comments")
export default class Comment extends Entity {
  constructor(comment: Partial<Comment>) {
    super();
    Object.assign(this, comment);
  }

  @Index()
  @Column()
  identifier: string;

  @Column()
  body: string;

  @Column()
  username: string;

  @ManyToOne(() => User)
  @JoinColumn({ name: "username", referencedColumnName: "username" })
  user: User;

  @ManyToOne(() => Post, post => post.comments, { nullable: false })
  post: Post;

  @OneToMany(() => Vote, vote => vote.comment)
  votes: Vote[];

  protected userVote: number;
  setUserVote(user: User) {
    const index = this.votes.findIndex(v => v.username === user.username);
    this.userVote = index > -1 ? this.votes[index].value : 0;
  }

  @BeforeInsert()
  makeIdAndSlug() {
    this.identifier = makeid(8);
  }
}

问题：所以，我有投票和评论之间的关系，问题是在投票实体中我们有这行代码@ManyToOne(() => Comment) comment: Comment;

在评论实体中，我们还有另一行代码 @OneToMany(() => Vote, vote => vote.comment) votes: Vote[];

目标：现在，为什么在 Vote 实体中我们只放置 () => 评论，插入 () => comment.votes ？我需要了解它及其功能，如果可以帮助我，我会感谢你！

感谢您的时间