我得到一个空数组答案

【问题标题】：I get an empty array我得到一个空数组
【发布时间】：2021-11-25 06:06:12
【问题描述】：

在尝试返回所有 cmets 以及对 cmets 的回复时，我遇到了问题

示例模板：

[
  {
    "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"
  }
]

所以，我得到了什么：

[
  {
    "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": {},
    "type": "COMMENT_TYPE"
  }
]

获取所有 cmets 的代码：

@Get('/:entityId/comments')
  async getAll(@Param('entityId') entityId: string): Promise<any> {
    const comments = await this.commentRepository.find({
      where: { entityId: entityId, replyId: null },
      order: { id: 'DESC' },
    });
    return comments.map(entity => this.mapper(entity));
  }

private async getReply(commentId: string) {
    const reply = this.commentRepository.find({ where: { replyId: commentId } });
    reply.then(items => console.log(items));
    return reply.then(items => items.map(entity => this.mapper(entity)));
  }

  private mapper(entity: Comment): CommentDto {
    return new CommentDto(
      entity.id,
      entity.content,
      entity.authorId,
      entity.entityId,
      entity.creatAt,
      this.getReply(entity.id),
      entity.type,
    );
  }

在 getReply 方法中，我使用控制台进行调试。这是里面出现的内容

[
  Comment {
    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'
  },
  Comment {
    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'
  },
  Comment {
    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'
  }
]
[]
[]
[
  Comment {
    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'
  }
]
[]

所以，在我得到“replyId”字段的响应中：= {}，有一个空对象。我该如何解决这个问题？

提前感谢您的回答！

【问题讨论】：

您能否将代码减少到所需的最低限度（没有任何数据库访问代码），因为您手头似乎已经有了模型？这将允许其他人快速测试您的代码并帮助您找到解决方案
控制台日志中似乎没有空对象..你的意思是空数组[]？
@ParvSharma 我复制了 IDE 控制台中的所有内容

标签： javascript arrays object async-await

【解决方案1】：

确保您在 CommentDto replyId 中没有任何类型。
然后不要使用。 Async / Await 想出了摆脱 .then。

解决方案：

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

private async getReply(commentId: string): Promise<CommentDto[]> {
    const reply = await this.commentRepository.find({ where: { replyId: commentId } });
    reply.then(items => console.log(items));
    return await Promise.all(reply.map(entity => this.mapper(entity)));
  }

  private mapper(entity: Comment): Promise<CommentDto> {
    return new CommentDto(
      entity.id,
      entity.content,
      entity.authorId,
      entity.entityId,
      entity.creatAt,
      await this.getReply(entity.id),
      entity.type,
    );
  }

【讨论】：