NodeJS 和 MongoDB - 将聚合和 $lookup 与 findById 一起使用

Question

我想建立两个集合之间的关系 - 一本书和作者集合。如果我只使用获取和显示我所有的书，并通过 id 集成关于作者的数据，它就可以工作。

作者架构：

 const AuthorSchema = new mongoose.Schema({
      name: { type: String, required: true },
      surname: { type: String, required: true },
      dateOfBirth: { type: String, required: true },
      countryOfBirth: { type: String, required: true },
      
    });

书籍架构：

const BookSchema = new mongoose.Schema({
   owner: { type: String, required: true },
   pagesNo: { type: String, required: true },
   releaseDate: { type: String, required: true }, 
   country: { type: String, required: true },
   authorID: { type: Schema.Types.ObjectId, ref: "Author", required: true }, <-- HERE I NEED DATA ABOUT AUTHOR
});

我的用于获取所有数据的快速函数：

 router.get("/", async (req, res) => {
   try {
     let books = await Book.aggregate([
       {
        $lookup: {
          from: "authors",
          localField: "authorID",
          foreignField: "_id",
          as: "author",
        },
      },
    ]);

    res.status(200).json(books);
  } catch (err) {
    res.status(404).json({ success: false, msg: "Book is not found" });
  }
});

但现在我想在按 ID (findById()) 搜索单本书时也显示连接的数据。如果我使用这样的函数，我会得到一个错误状态：

router.get("/:bookId", async (req, res) => {
  try {
    let book= await Book.aggregate([
      {
       $lookup: {
              from: "authors",
              localField: "authorID",
              foreignField: "_id",
              as: "author",
            },
      },
    ]);
    book= book.findById({ _id: req.params.bookId});
    res.status(200).json(book);
  } catch (err) {
    res.status(404).json({ success: false, msg: "Book is not found" });
  }
});

感谢您的帮助

Answer 1

使用 $match 只为同一查询查找一本书

const mongoose = require('mongoose');
const ObjectId = mongoose.Types.ObjectId();

    router.get("/:bookId", async (req, res) => {
          try {
            let book= await Book.aggregate([
              {
                $match: { _id : ObjectId("book _id") }
              },
              {
               $lookup: {
                      from: "authors",
                      localField: "authorID",
                      foreignField: "_id",
                      as: "author",
                    },
              },
            ]);
            book= book.findById({ _id: req.params.bookId});
            res.status(200).json(book);
          } catch (err) {
            res.status(404).json({ success: false, msg: "Book is not found" });
          }
        });

NodeJS 和 MongoDB - 将聚合和 $lookup 与 findById 一起使用

NodeJS and MongoDB - use aggregate and $lookup together with findById

node.js

mongodb

express

mongoose