mongoose.connection()和mongoose.createConnection()之间的混淆 [英] Confusion between mongoose.connection() and mongoose.createConnection()

问题描述

我研究猫鼬已经三天了，对这两种方法的使用我有点困惑(我知道将来会不推荐使用"mongoose.connection()" ...)

I've been studying mongoose for three days and I'm a bit confused about the use of these two methods (i know that "mongoose.connection()" will be deprecated in the future...)

问题是:当我尝试转换(从"mongoose.connection()"到"mongoose.createConnection()")时，此示例的action.js文件

The problem is: when I'm trying to convert (from "mongoose.connection()" to "mongoose.createConnection()") the action.js file of this example https://gist.github.com/2785463 it seems to not work for me...

有我的代码...

var mongoose = require('mongoose'),
db = mongoose.createConnection('localhost', 'test');

db.on('error', function () {
  console.log('Error! Database connection failed.');
});

db.once('open', function (argument) {
  console.log('Database connection established!');

  mongoose.connection.db.collectionNames(function (error, names) {
    if (error) {
      console.log('Error: '+ error);
    } else {
      console.log(names);
    };
  });
});

还有我的终端输出(在我的ubuntu终端上键入"node test.js".)

and there's my terminal output (typing "node test.js" on my ubuntu terminal..)

Database connection established!

/home/_user_/Scrivania/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connection/server.js:437
    throw err;
          ^
TypeError: Cannot call method 'collectionNames' of undefined
  at NativeConnection.<anonymous> (/home/_user_/Scrivania/test2.js:11:25)
  at NativeConnection.g (events.js:192:14)
  at NativeConnection.EventEmitter.emit (events.js:93:17)
  at open (/home/_user_/Scrivania/node_modules/mongoose/lib/connection.js:408:10)
  at NativeConnection.Connection.onOpen (/home/_user_/Scrivania/node_modules/mongoose/lib/connection.js:415:5)
  at Connection._open (/home/_user_/Scrivania/node_modules/mongoose/lib/connection.js:386:10)
  at NativeConnection.doOpen (/home/_user_/Scrivania/node_modules/mongoose/lib/drivers/node-mongodb-native/connection.js:47:5)
  at Db.open (/home/_user_/Scrivania/node_modules/mongoose/node_modules/mongodb/lib/mongodb/db.js:287:14)
  at Server.connect.connectCallback (/home/_user_/Scrivania/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connection/server.js:235:7)
  at g (events.js:192:14)

推荐答案

如果不调用mongoose.connect()，则mongoose.connection不包含打开的连接.您应该使用mongo.createConnection()调用中的返回值(已保存到db中).

If you don't call mongoose.connect() then mongoose.connection doesn't contain an an open connection. You should be using the return value from your mongo.createConnection() call instead (that you've saved into db).

因此，代码的最后一部分应更改为:

So the last section of code should change to:

已更新

db.db.collectionNames(function (error, names) {
  if (error) {
    console.log('Error: '+ error);
  } else {
    console.log(names);
  };
});

我在Connection上看不到collectionNames方法；看来您必须遵循属性到本机连接对象中才能访问该对象(请参见上面的代码).

I don't see a collectionNames method on Connection; looks like you have to follow properties down into the native connection object to access that (see above code).

这篇关于mongoose.connection()和mongoose.createConnection()之间的混淆的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！