如何从另一个模型中找到另一个模型值？答案

【问题标题】：how to get find another model values from another model?如何从另一个模型中找到另一个模型值？
【发布时间】：2020-06-15 20:50:18
【问题描述】：

我想查找用户模型值并希望将该值存储在我当前的博客模型中

exports.getAllBlogs = async (req, res) => {
  try {
    const blogs = await Blog.find()
      .sort({ created_at: -1 })
      .populate({
        path: "comments"
      })
      .exec();
    const myblogs = blogs.map(async blog => {
      const user = await User.findOne({ _id: blog.author });
      return (blog.authorName = user.name);
    });
    console.log(myblogs);

    if (blogs.length === 0) {
      return res.status(404).json({ message: "No Blogs Found" });
    }

    return res.status(200).json(myblogs);
  } catch (error) {
    console.log(error);

    res.status(500).json({ error: "Something went wrong" });
  }
};

但这是回报我 [ Promise { } ] 对于每个集合

我怎样才能做到这一点，或者有没有更好的方法来做到这一点？

【问题讨论】：

标签： javascript node.js mongodb mongoose nosql

【解决方案1】：

您无需地图即可通过填充获取所有相关信息。

exports.getAllBlogs = async (req, res) => {
  try {
    const blogs = await Blog.find({})
      .sort({ created_at: -1 })
      .populate("author", "-password")
      .populate({
        path: "comments",
        populate: {
          path: "user",
          select: "-password"
        }
      });

    return res.status(200).json(blogs);
  } catch (error) {
    console.log(error);
    res.status(500).json({ error: "Something went wrong" });
  }
};

这将给出如下示例结果：

[
    {
        "_id": "5e53b2896f41c765fc4defa1",
        "title": "Blog2 Title",
        "body": "Blog2 Body",
        "author": {
            "_id": "5e53b1726f41c765fc4def9c",
            "email": "user1@gmail.com",
            "name": "User1",
            "created_at": "2020-02-24T11:20:18.343Z",
            "updated_at": "2020-02-24T11:20:18.343Z",
            "id": "5e53b1726f41c765fc4def9c"
        },
        "created_at": "2020-02-24T11:24:57.078Z",
        "updated_at": "2020-02-24T11:24:57.078Z",
        "__v": 0,
        "comments": [
            {
                "_id": "5e53b34c6f41c765fc4defa5",
                "body": "Comment3 (user2 on user1's blog2)",
                "user": {
                    "_id": "5e53b1906f41c765fc4def9d",
                    "email": "user2@gmail.com",
                    "name": "User2",
                    "created_at": "2020-02-24T11:20:48.070Z",
                    "updated_at": "2020-02-24T11:20:48.070Z",
                    "__v": 0,
                    "id": "5e53b1906f41c765fc4def9d"
                },
                "blog": "5e53b2896f41c765fc4defa1",
                "created_at": "2020-02-24T11:28:12.551Z",
                "updated_at": "2020-02-24T11:28:12.551Z"
            }
        ],
        "id": "5e53b2896f41c765fc4defa1"
    },
    {
        "_id": "5e53b26c6f41c765fc4def9f",
        "title": "Blog1 Title",
        "body": "Blog1 Body",
        "author": {
            "_id": "5e53b1726f41c765fc4def9c",
            "email": "user1@gmail.com",
            "name": "User1",
            "created_at": "2020-02-24T11:20:18.343Z",
            "updated_at": "2020-02-24T11:20:18.343Z",
            "id": "5e53b1726f41c765fc4def9c"
        },
        "created_at": "2020-02-24T11:24:28.895Z",
        "updated_at": "2020-02-24T11:24:28.895Z",
        "__v": 0,
        "comments": [
            {
                "_id": "5e53b2f86f41c765fc4defa3",
                "body": "Comment1 (user2 on user1's blog1)",
                "user": {
                    "_id": "5e53b1906f41c765fc4def9d",
                    "email": "user2@gmail.com",
                    "name": "User2",
                    "created_at": "2020-02-24T11:20:48.070Z",
                    "updated_at": "2020-02-24T11:20:48.070Z",
                    "id": "5e53b1906f41c765fc4def9d"
                },
                "blog": "5e53b26c6f41c765fc4def9f",
                "created_at": "2020-02-24T11:26:48.506Z",
                "updated_at": "2020-02-24T11:26:48.506Z"
            },
            {
                "_id": "5e53b3246f41c765fc4defa4",
                "body": "Comment2 (user3 on user1's blog1)",
                "user": {
                    "_id": "5e53b1996f41c765fc4def9e",
                    "email": "user3@gmail.com",
                    "name": "User3",
                    "created_at": "2020-02-24T11:20:57.488Z",
                    "updated_at": "2020-02-24T11:20:57.488Z",
                    "id": "5e53b1996f41c765fc4def9e"
                },
                "blog": "5e53b26c6f41c765fc4def9f",
                "created_at": "2020-02-24T11:27:32.305Z",
                "updated_at": "2020-02-24T11:27:32.305Z"
            }
        ],
        "id": "5e53b26c6f41c765fc4def9f"
    }
]

【讨论】：

【解决方案2】：

因为您在地图中使用异步。这将返回 Promises 数组。

试试这个

const myblogs = await Promise.all(
  blogs.map(async blog => {
      const user = await User.findOne({ _id: blog.author });
      blog.authorName = user.name;
      return blog;
   })
);

【讨论】：

这行得通，但现在我只得到名字，然后我更改了一些代码` const myblogs = await Promise.all( blogs.map(async blog => { const user = await User.findOne({ _id : blog.author }); blog.author = user.name; return blog; }) );` 但它没有返回它返回相同值的值有没有更好的方法来实现这一点，比如查询或可以得到每个博客作者姓名和 ID？
blog.authorName = user.name 与 blog.author = user.name; return blog; 不同。可能是错误？你需要blog.**authorName** = user.name; return blog;