Question

我有这段代码

var MongoClient = require('mongodb').MongoClient
  , assert = require('assert');

// Connection URL 
var url = 'mongodb://user:pwd@lo037234.mlab.com:37234/heroku_plpzj3t5j';
// Use connect method to connect to the Server 
MongoClient.connect(url, function(err, db) {
  assert.equal(null, err);
  console.log("Connected correctly to server");

db.collection('members', function(err, collection) {
  collection.find({}, function(err, cursor) {
    cursor.each(function(err, item) {
      console.log(item.telephoneNumber);

    });

    // our collection has returned, now we can close the database
    db.close();
  });
});
});

我用来列出集合成员中的所有电话号码。

然而，代码列出了数字，然后显示这样的错误

Connected correctly to server
0820069005
0920069005ww
0220929975
/home/obulex/node_modules/mongodb/lib/utils.js:98
    process.nextTick(function() { throw err; });
                                  ^

TypeError: Cannot read property 'telephoneNumber' of null
    at /home/obulex/workers/actors/actor.js:14:23
    at handleCallback (/home/obulex/node_modules/mongodb/lib/utils.js:96:12)
    at /home/obulex/node_modules/mongodb/lib/cursor.js:741:16
    at handleCallback (/home/obulex/node_modules/mongodb/lib/utils.js:96:12)
    at /home/obulex/node_modules/mongodb/lib/cursor.js:675:5
    at handleCallback (/home/obulex/node_modules/mongodb-core/lib/cursor.js:172:5)
    at setCursorDeadAndNotified (/home/obulex/node_modules/mongodb-core/lib/cursor.js:507:3)
    at nextFunction (/home/obulex/node_modules/mongodb-core/lib/cursor.js:651:7)
    at Cursor.next [as _next] (/home/obulex/node_modules/mongodb-core/lib/cursor.js:692:3)
    at nextObject (/home/obulex/node_modules/mongodb/lib/cursor.js:672:8)

为什么我在代码结尾处收到错误？

Answer 1

问题是您的代码在find（）方法中执行回调。

根据API，collection.find（）返回一个Cursor对象： http://mongodb.github.io/node-mongodb-native/2.0/api/Collection.html#find

根据上面链接中显示的一些示例或下面链接的教程尝试重构代码： https://docs.mongodb.com/getting-started/node/query/#query-for-all-documents-in-a-collection

正如Henrique所说，由于原始提交中包含的敏感信息，您可能希望删除此问题。

Answer 2

这终于奏效了

var MongoClient = require('mongodb').MongoClient
  , assert = require('assert');

// Connection URL 
var url = 'mongodb://logan:password32@username32.mlab.com:37234/heroku_xpzj3t5j';
// Use connect method to connect to the Server 
MongoClient.connect(url, function(err, db) {
  assert.equal(null, err);
  console.log("Connected correctly to server");

   var cursor = db.collection('members').find( );
   cursor.each(function(err, doc) {
      assert.equal(err, null);
      if (doc != null) {
         console.log(doc.telephoneNumber);
      } else {
         //callback();
      }
   });

});

在集合中列出mongodb文档会引发错误

2 个答案: