Populate in mongoose

query

var mongoose = require('mongoose');
var Event = mongoose.model('Event');
var Calendar = mongoose.model('Calendar'); 

function eventController(app) {

  app.get('/calendar/:calendarid', function (req, res) {
		    Calendar
		    .findOne({ _id:req.params.calendarid })
		    .populate('events')
		    .exec(function (err, data) {
		    	console.log("executing populate");
		      if (err) {
		        return res.json({error:err})
		      }
		      return res.json(data)
		    })
		});	

exports.boot = eventController;	  

schemas

// Calendar model/schema in one file

exports.boot = function(mongoose) {
  var Schema = mongoose.Schema;
  var ObjectId = Schema.ObjectId;
  
  var Calendar = new Schema({
    creator : { type: Schema.ObjectId, ref: 'User'},
    name : { type: String, index:true },
    description : String,
    events : [{ type: Schema.ObjectId, ref: 'Event'}],
    group: [{ type: Schema.ObjectId, ref: 'Group'}],
    date : { type : Date, default:Date.now }
  });

  mongoose.model('Calendar', Calendar);
  
}

// And in another file the event model/schema

exports.boot = function(mongoose) {
  var Schema = mongoose.Schema;
  var ObjectId = Schema.ObjectId;

  var Event= new Schema({
    creator : { type: Schema.ObjectId, ref: 'User'},
    name : { type: String, index:true },
    description : String,
    attendees : [{ type: Schema.ObjectId, ref: 'User'}],
    calendar : { type: Schema.ObjectId, ref: 'Calendar'},
    date : { type: Date, default: Date.now}
  });

 
  mongoose.model('Event', Event);
}