获取带有答案的评论列表答案

【问题标题】：get a list of comments with answers获取带有答案的评论列表
【发布时间】：2021-11-24 20:42:45
【问题描述】：

我在文章上有 cmets。但我决定稍微扩展评论的可能性，添加回复评论的功能。

评论实体：

@Entity()
export class Comment {
  @PrimaryColumn()
  id: string;

  @Column({ type: 'varchar', length: 50 })
  content: string;

  @Column()
  authorId: string;

  @Column()
  entityId: string;

  @CreateDateColumn()
  creatAt: Date;

  @Column('text', { nullable: true })
  replyId?: string;

  @Column({ type: 'enum', enum: CommentTypeEnum })
  type: CommentTypeEnum;
}

一些细节：当我创建对评论的回复时，我会获取父评论的 id（我回复的评论）并将其写入 replyId。父级可以有 NULL 也可以包含一个 id。简而言之，一条新评论包含其父级的 id。

[
  {
    "id": "dee96b97-cd45-4a09-a27d-985617cc5a16",
    "content": "comment",
    "authorId": "a30bfd0b-0519-4b4f-bbc5-04178f8af782",
    "entityId": "91e22cb7-cb42-49a3-a5e7-8d111111",
    "creatAt": "2021-10-04T08:43:35.204Z",
    "replyId": "cab2d3fd-7fba-4d02-a911-538246d92cfd",
    "type": "COMMENT_TYPE"
  },
  {
    "id": "d61e0049-9075-4f25-8f6d-65ed61e245a8",
    "content": "comment",
    "authorId": "a30bfd0b-0519-4b4f-bbc5-04178f8af782",
    "entityId": "91e22cb7-cb42-49a3-a5e7-8d111111",
    "creatAt": "2021-10-04T08:43:21.271Z",
    "replyId": "4f7b2bb3-b224-45d9-8093-9c0de7514bd4",
    "type": "COMMENT_TYPE"
  },
  {
    "id": "cab2d3fd-7fba-4d02-a911-538246d92cfd",
    "content": "comment",
    "authorId": "a30bfd0b-0519-4b4f-bbc5-04178f8af782",
    "entityId": "91e22cb7-cb42-49a3-a5e7-8d111111",
    "creatAt": "2021-10-04T08:43:22.663Z",
    "replyId": "4f7b2bb3-b224-45d9-8093-9c0de7514bd4",
    "type": "COMMENT_TYPE"
  },
  {
    "id": "4f7b2bb3-b224-45d9-8093-9c0de7514bd4",
    "content": "comment",
    "authorId": "a30bfd0b-0519-4b4f-bbc5-04178f8af782",
    "entityId": "91e22cb7-cb42-49a3-a5e7-8d111111",
    "creatAt": "2021-10-04T08:43:04.391Z",
    "replyId": null,
    "type": "COMMENT_TYPE"
  },
  {
    "id": "1ea5cdcb-2f19-4b00-94e0-5b245bb91237",
    "content": "comment",
    "authorId": "a30bfd0b-0519-4b4f-bbc5-04178f8af782",
    "entityId": "91e22cb7-cb42-49a3-a5e7-8d111111",
    "creatAt": "2021-10-04T08:43:22.094Z",
    "replyId": "4f7b2bb3-b224-45d9-8093-9c0de7514bd4",
    "type": "COMMENT_TYPE"
  }
]

获取特定记录的所有记录的方法：

@Get('/:entityId/comments')
  async getAll(@Param('entityId') entityId: string): Promise<CommentDto[]> {
    const comments = await this.commentRepository.find({ where: { entityId: entityId }, order: { id: 'DESC' } });
    return comments.map(it => ({
      id: it.id,
      content: it.content,
      authorId: it.authorId,
      entityId: it.entityId,
      creatAt: it.creatAt,
      replyId: it.replyId || null,
      type: it.type,
    }));
  }

DTO：

export class CommentDto {
  id: string;
  content: string;
  authorId: string;
  entityId: string;
  creatAt: Date;
  replyId?: string;
  type: CommentTypeEnum;
}

如何获取记录，如下例所示：

[
  {
    "id": "4f7b2bb3-b224-45d9-8093-9c0de7514bd4",
    "content": "comment",
    "authorId": "a30bfd0b-0519-4b4f-bbc5-04178f8af782",
    "entityId": "91e22cb7-cb42-49a3-a5e7-8d111111",
    "creatAt": "2021-10-04T08:43:04.391Z",
    "replyId": [
        {
          "id": "cab2d3fd-7fba-4d02-a911-538246d92cfd",
          "content": "comment",
          "authorId": "a30bfd0b-0519-4b4f-bbc5-04178f8af782",
          "entityId": "91e22cb7-cb42-49a3-a5e7-8d111111",
          "creatAt": "2021-10-04T08:43:22.663Z",
          "replyId": [
              {
                "id": "dee96b97-cd45-4a09-a27d-985617cc5a16",
                "content": "comment",
                "authorId": "a30bfd0b-0519-4b4f-bbc5-04178f8af782",
                "entityId": "91e22cb7-cb42-49a3-a5e7-8d111111",
                "creatAt": "2021-10-04T08:43:35.204Z",
                "replyId": "cab2d3fd-7fba-4d02-a911-538246d92cfd",
                "type": "COMMENT_TYPE"
              }
            ],
          "type": "COMMENT_TYPE"
        },
        {
          "id": "d61e0049-9075-4f25-8f6d-65ed61e245a8",
          "content": "comment",
          "authorId": "a30bfd0b-0519-4b4f-bbc5-04178f8af782",
          "entityId": "91e22cb7-cb42-49a3-a5e7-8d111111",
          "creatAt": "2021-10-04T08:43:21.271Z",
          "replyId": "4f7b2bb3-b224-45d9-8093-9c0de7514bd4",
          "type": "COMMENT_TYPE"
        },
        {
          "id": "cab2d3fd-7fba-4d02-a911-538246d92cfd",
          "content": "comment",
          "authorId": "a30bfd0b-0519-4b4f-bbc5-04178f8af782",
          "entityId": "91e22cb7-cb42-49a3-a5e7-8d111111",
          "creatAt": "2021-10-04T08:43:22.663Z",
          "replyId": "4f7b2bb3-b224-45d9-8093-9c0de7514bd4",
          "type": "COMMENT_TYPE"
        },
        {
          "id": "1ea5cdcb-2f19-4b00-94e0-5b245bb91237",
          "content": "comment",
          "authorId": "a30bfd0b-0519-4b4f-bbc5-04178f8af782",
          "entityId": "91e22cb7-cb42-49a3-a5e7-8d111111",
          "creatAt": "2021-10-04T08:43:22.094Z",
          "replyId": "4f7b2bb3-b224-45d9-8093-9c0de7514bd4",
          "type": "COMMENT_TYPE"
        }
      ],
    "type": "COMMENT_TYPE"
  }
]

提前感谢您的回答

【问题讨论】：

标签： arrays database typescript list typeorm

【解决方案1】：

查找 TypeOrm 的“多对一”关系 (https://orkhan.gitbook.io/typeorm/docs/many-to-one-one-to-many-relations)。

实际上，你想要：

@ManyToOne(type => Comment)
@JoinColumn({ name: 'replyId' })
reply?: Comment | null;

@Column({ nullable: true })
@Index()
replyId: string | null;

然后使用：

await this.commentRepository.find({
    where: { entityId: entityId },
    relations: ['reply'],
    order: { id: 'DESC' }
});

快速警告，默认情况下 typeorm 不会将所有关系获取到无限深度。 relations: ['reply'] 将深入一层。 relations: ['reply', 'reply.reply', 'reply.reply.reply'] 将上升到 3（但越往上越慢）。

【讨论】：