从mongo检索文件时，this.db.collection不起作用

Question

我正在尝试从mongodb地图集中检索一个文件，我使用的是gridfsstream，multer.It一直给我这个错误。

TypeError: this.db.collection不是一个函数

我可以成功上传，但检索不是working.What，我在这里失踪了吗？

const router = require("express").Router();
const multer = require("multer");
const { mongo, connection } = require("mongoose");
const config = require("../../config/main").db;
const Grid = require("gridfs-stream");
Grid.mongo = mongo;
var gfs = Grid(config);

// set up connection to db for file storage
const storage = require("multer-gridfs-storage")({
  url: config,
  file: (req, file) => {
    return {
      filename: file.originalname
    };
  }
});
// sets file input to single file
const singleUpload = multer({ storage: storage }).single("file");



  router.get("/files", (req, res) => {
  gfs.files.find().toArray((err, files) => {
    if (!files || files.length === 0) {
      return res.status(404).json({
        message: "Could not find files"
      });
    }
    return res.json(files);
  });

Answer 1

我希望还能帮助你，虽然过了几天！当我试图检索一个图像时，我也犯了同样的错误。下面是我的代码：

  MongoClient.connect(config.Info.mongo_database, {}, (err, client) => {
        if(err) { new Error("An error has occurred while this file is retrieving: "+ err); }

        //throw the error: this.db.collection is not a function
        let bucket = new mongo.GridFSBucket(client.db,  {
          bucketName: bucketName
        });

        bucket.openDownloadStreamByName(filename).pipe(response);
      })

我就这样解决了：

  MongoClient.connect(config.Info.mongo_database, {}, (err, client) => {
        if(err) { new Error("An error has occurred while this file is retrieving: "+ err); }

        //Look this, I must to explicit database name, otherwise that error is thrown
        let db = client.db('files_repository');

        let bucket = new mongo.GridFSBucket(db,  {
          bucketName: bucketName
        });

        bucket.openDownloadStreamByName(filename).pipe(response);
      })

现在对我有用了！！