获取Node.js和MongoDB中的收集数据

Question

Tell me please, how can I create REST API using backbone application on the client and nodejs + mongodb in the server side.

I am new in nodejs and can't understand all of the elementary things.

Just for example — I need to get friends collection. In my client app I say

var collection = new Backbone.Collection.exted({ 
  model: model,
  url: '/api/friends'
});
collection.fetch();

Ok, on the server (nodejs + express) I can listen this request with app.get('/api/friends', friends.get);

in the «friends» module I have «get» function. It connect to database, try to get data from «friends» collection (if collection is not exist it must be create). If collection is empty, function must to initialize request to the vk.com (social netword) server for its data.

/*
 * GET friends
 */
var https = require('https'),
  Db = require('mongodb').Db,
  Server = require('mongodb').Server;

var client = new Db('data', new Server('127.0.0.1', 27017, {})),
  friends;

function getAllFriends(err, collection) {
  if (!collection.stats()) {
    https.get('https://api.vk.com/method/friends.get?access_token=' + global['access_token'], function (d) {
      var chunk = '',
        response;
      d.on('data', function (data) {
        chunk += data;
      });

      d.on('end', function () {
        response = JSON.parse(chunk).response;
        response.forEach(function (friend) {
          collection.insert(friend, function (err, docs) {
            if (err) console.log(err);
          });
        });
      }).on('error', function (e) {
        console.error(e);
      });
    });
  }

  friends = collection.find({}, {
    limit: 1000
  }).toArray(function (err, docs) {
    return docs;
  });
}

exports.get = function (req, res) {
  client.open(function (err, pClient) {
    client.collection('friends', getAllFriends);
    res.send(friends);
  });
};

But this code don't work. I have no idea why.

/node_modules/mongodb/lib/mongodb/connection/server.js:524
        throw err;
              ^
TypeError: Cannot read property 'noReturn' of undefined
    at Cursor.nextObject.commandHandler (/node_modules/mongodb/lib/mongodb/cursor.js:623:17)
    at Db._executeQueryCommand (/node_modules/mongodb/lib/mongodb/db.js:1702:5)
    at g (events.js:192:14)
    at EventEmitter.emit (events.js:126:20)
    at Server.Base._callHandler (/node_modules/mongodb/lib/mongodb/connection/base.js:130:25)
    at Server.connect.connectionPool.on.server._serverState (/node_modules/mongodb/lib/mongodb/connection/server.js:517:20)
    at MongoReply.parseBody (/node_modules/mongodb/lib/mongodb/responses/mongo_reply.js:127:5)
    at Server.connect.connectionPool.on.server._serverState (/node_modules/mongodb/lib/mongodb/connection/server.js:476:22)
    at EventEmitter.emit (events.js:96:17)
    at _connect (/node_modules/mongodb/lib/mongodb/connection/connection_pool.js:175:13)

Maybe this code is not creating collection when it needs?

Maybe I do wrong anything, so can you give me a good link to read tutorial in nodejs or mongo.

Thanks for your advice and sorry please for my english.

Answer 1

There is a lot of code that just doesn't work here. Take this for example:

 if (!collection.stats()) {
    fetchFriends().forEach(function (friend) {
      collection.insert(friend, function (err, docs) {
        if (err) console.log(err);
      });
    });
  }

  friends = collection.find({}, {
    limit: 1000
  }).toArray(function (err, docs) {
    return docs;
  });
}

For a start you can't do it like that with fetchFriends. That function doesn't return anything, all the work is done in async callbacks.

Secondly if it's empty, you're still triggering a call to find directly and not waiting till the results of your insert finish.

Even the beginning of the call chain is broken:

exports.get = function (req, res) {
  client.open(function (err, pClient) {
    client.collection('friends', getAllFriends);
    res.send(friends);
  });
};

You can't just call res.send after calling client.colleciton , you need to do this in a callback after the work gets done in getAllFriends.

There is a general lack of understanding of async code throughout what you're doing, I think dont worry about node/mongo tutorials for now, rather play with node more first, and have a look at the async library and promises until you're comfortable with async.

Answer 2

I have no idea what this code is supposed to do.

• Reduce the amount of code you are debugging ;
• identify clearly what is not giving you what you are expecting ;
• use console.log

you'll probably first find that :

exports.get = function (req, res) {
  client.open(function (err, pClient) {
    client.collection('friends', getAllFriends);
    res.send(friends);
  });
};

doesn't work because the variable "friends" is not what you expect it to be.