Gerting 錯誤 db.collection 不是函數？

Question

我在 mongodb 中使用 socket.io 和 nodejs/express。 在 server.js 中，我將數據存儲在 mongodb 中，但出現錯誤 db.collection is not a function 為什么會這樣？

我已經看到這個問題 -> db.collection is not a function when using MongoClient v3.0但我無法理解如何修改我的代碼以便它可以工作？ 我應該將所有代碼移到.then()嗎？

代碼：

服務器.js：

const express = require('express');
const mongoose = require('mongoose');
const socket = require('socket.io');
const message = require('./model/message')

const app = express();

const db = require('./config/keys').mongoURI;

mongoose.connect(db, {useNewUrlParser: true})
  .then(() => console.log('Mongodb connected...'))
  .catch( err => console.log(err));

const port = 5000;

let server = app.listen(5000, function(){
  console.log('server is running on port 5000')
});

let io =  socket(server);

io.on("connection", function(socket){
  console.log("Socket Connection Established with ID :"+ socket.id)

  socket.on('disconnect', function(){
    console.log('User Disconnected');
  });

  let chat = db.collection('chat');  <---GETTING ERROR HERE

      socket.on('SEND_MESSAGE', function(data){
        let message = data.message;
        let date = data.date;

        // Check for name and message
        if(name !== '' || date !== ''){
            // Insert message
            chat.insert({message: message, date:date}, function(){
                socket.emit('output', [data]);
            });
        }
    });

    chat.find().limit(100).sort({_id:1}).toArray(function(err, res){
      if(err){
          throw err;
      }
      // Emit the messages
      socket.emit('RECEIVE_MESSAGE', res);
    });

})

注意：我的 mongo 版本是 4

Answer 1

您需要將連接傳遞給 db 對象，如下所示

const mongoURI = require('./config/keys').mongoURI;

mongoose.connect(mongoURI, {useNewUrlParser: true}

db = mongoose.connection;

db.on('error', console.error.bind(console, 'connection error:'));

db.once('open', function() {
console.log('Mongodb connected...')
});

在此之后，您就可以使用db對象了。 然后創建schmea和models並使用它來插入或查詢數據。 在你的情況下，它是一個chat模型。

看來你對mongoose用法不太清楚，所以我建議你先閱讀文檔： https : //mongoosejs.com/docs/index.html

Answer 2

嘗試一下

const url = "mongodb://<dbuser>:<dbpassword>@ds141633.mlab.com:41633/mongochat";
const options = const options = {

  useNewUrlParser: true,

  autoIndex: false, // Don't build indexes

  reconnectTries: Number.MAX_VALUE, // Never stop trying to reconnect

  reconnectInterval: 1000, // Reconnect every 500ms

  poolSize: 10, // Maintain up to 10 socket connections

  // If not connected, return errors immediately rather than waiting for reconnect
  bufferMaxEntries: 0,

  connectTimeoutMS: 10000, // Give up initial connection after 10 seconds

  socketTimeoutMS: 45000, // Close sockets after 45 seconds of inactivity
  family: 4 // Use IPv4, skip trying IPv6

};

// 連接數據庫...

**

mongoose.connect(url, options).then(
  () => {
    console.log('database connected');
  },
  err => console.log(err)
);
mongoose.Promise = global.Promise;

**