Mongoskin will not fetch some results from mongodb in nodejs app

Question

I wanted to read some data from a mongodb via mongoskin. But nodejs throws me an error when i try to call localhost:3000/tasks

In my database 'todo' there are some items in the collection 'tasks'. The result in the console works fine when i start the app.

Can anyone see where i wrote something wrong?

The eroor message:

500 TypeError: Cannot read property 'tasks' of undefined
at exports.list (/Users/piet/Websites/privat/mongo/routes/tasks.js:7:8) at callbacks     (/Users/piet/Websites/privat/mongo/node_modules/express/lib/router/index.js:164:37)
at param (/Users/piet/Websites/privat/mongo/node_modules/express/lib/router/index.js:138:11)
at pass (/Users/piet/Websites/privat/mongo/node_modules/express/lib/router/index.js:145:5)
at Router._dispatch    (/Users/piet/Websites/privat/mongo/node_modules/express/lib/router/index.js:173:5)
at Object.router   (/Users/piet/Websites/privat/mongo/node_modules/express/lib/router/index.js:33:10)
at next   (/Users/piet/Websites/privat/mongo/node_modules/express/node_modules/connect/lib/proto.js:193:    15)
at Object.methodOverride [as handle]  (/Users/piet/Websites/privat/mongo/node_modules/express/node_modules/connect/lib/middleware/me    thodOverride.js:48:5)
at next (/Users/piet/Websites/privat/mongo/node_modules/express/node_modules/connect/lib/proto.js:193:    15)
at Object.urlencoded [as handle]   (/Users/piet/Websites/privat/mongo/node_modules/express/node_modules/connect/lib/middleware/ur    lencoded.js:49:37)

My app.js:

var express = require('express');
var routes = require('./routes');
var tasks = require('./routes/tasks');
var http = require('http');
var path = require('path');

var mongo = require("mongoskin");
var db = mongo.db('localhost:27017/todo?auto_reconnect=true', { 
safe:true })
.collection('tasks')
.find()
.toArray(function(error, items){
    console.log(items);
})

var app = express();
app.set('port', process.env.PORT || 3000);
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
app.use(express.favicon());
app.use(express.logger('dev'));
app.use(express.json());
app.use(express.urlencoded());
app.use(express.methodOverride());
app.use(app.router);
app.use(express.static(path.join(__dirname, 'public')));

if ('development' == app.get('env')) {
   app.use(express.errorHandler());
}
app.get('/', routes.index);
app.get('/tasks', tasks.list);
http.createServer(app).listen(app.get('port'), function(){
  console.log('Express server listening on port ' + app.get('port'));
});

The route file under /routes/tasks.js

exports.list = function(req, res, next){
req.db.tasks.find({
    completed: false
}).toArray(function(error, tasks){
    res.render('tasks', {
        title: "ToDo list",
        name: tasks = tasks || []
    })
})
};

Answer 1

In your routes/task.js, req is Express.js's request object. It doesn't have "db" handle, that's why you are getting error:

500 TypeError: Cannot read property 'tasks' of undefined

In app.js, this is the incorrect way of getting the db handle:

var mongo = require("mongoskin");
var db = mongo.db('localhost:27017/todo?auto_reconnect=true', { safe:true })
   .collection('tasks')
   .find()
   .toArray(function(error, items){
       console.log(items);
   });

db code should be moved into a separate module (dbConnection.js for instance) so that every time you need the db handle, you just need to do this:

var db = require('./dbConnection').getDb();

routes/task.js needs to get the db handle to make database call. So here are your revised app.js, routes/task.js and new dbConnection.js files:

dbConnection.js:

var open = function() {
    return require('mongoskin').db('localhost:27017/todo?auto_reconnect=true',
        {safe: true, strict: false}
    );
};

var db = open();

var dbConnection = {
    getDb: function() {
        if (!db) {
           db = open();
        }
        return db;
    }
};

module.exports = dbConnection;

routes/task.js:

var db = require('../dbConnection').getDb();

exports.list = function(req, res, next){
    var tasksCollection = db.collection('tasks');

    tasksCollection.find({ completed: false }).toArray(function(error, tasks){
        res.render('tasks', {
            title: "ToDo list",
            name: (tasks || [])
        });
    });
};

app.js:

var express = require('express');
var routes = require('./routes');
var tasks = require('./routes/tasks');
var http = require('http');
var path = require('path');

var app = express();
app.set('port', process.env.PORT || 3000);
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
app.use(express.favicon());
app.use(express.logger('dev'));
app.use(express.json());
app.use(express.urlencoded());
app.use(express.methodOverride());
app.use(app.router);
app.use(express.static(path.join(__dirname, 'public')));

if ('development' == app.get('env')) {
    app.use(express.errorHandler());
}
app.get('/', routes.index);
app.get('/tasks', tasks.list);
http.createServer(app).listen(app.get('port'), function(){
    console.log('Express server listening on port ' + app.get('port'));
});

Answer 2

You're going to need a middleware to hook up the collection object to your requests:

var db    = mongo.db('localhost:27017/todo?auto_reconnect=true');
var tasks = db.collection('tasks');
...
app.use(function(req, res, next) {
  req.db = { tasks : tasks }; // this exposes the collection as `req.db.tasks`
                              // to your route handlers
  next();
});
app.use(app.router);
...

Answer 3

Use 28017 as port id. You can check what you are getting in "req.db". Mayb this is undefined.