node.js - 类型错误 : Cannot read property 'findOne' of undefined

Question

代码如下

var mongo = require('mongodb');

var databaseName = 'Starter',
    collectionName = 'wines';

var Server = mongo.Server,
    Db = mongo.Db,
    BSON = mongo.BSONPure;

db = new Db(databaseName, server);

db.open(function(err, db) {
  if(!err) {
    console.log("Connected to 'winedb' database");
    db.collection(collectionName, {strict:true}, function(err, collection) {
        if (err) {
            console.log("The 'wines' collection doesn't exist. Creating it with sample data...");
            populateDB();
        }
    });
  }
});

exports.findById = function(req, res) {
  var id = req.params.id;
  console.log('Retrieving wine: ' + id);

  db.collection(collectionName, function(err, collection) {
      collection.findOne({'_id':new BSON.ObjectID(id)}, function(err, item) {
          res.send(item);
      });
  });

};

这些代码基于带有 mongoDB 的 nodejs 的 restful api 示例。 但是，它似乎无法识别函数findOne。有人可以指出问题吗？

错误信息:

TypeError: Cannot read property 'findOne' of undefined

Answer 1

findOne is deprecated in the latest version of mongodb@2.x

https://github.com/mongodb/node-mongodb-native/blob/2.0/lib/collection.js

您可以改用此查询

find(query).limit(1).next(function(err, doc){
   // handle data
})