How to set Backbone Model.idAttribute?

Question

I'm using MongoDb/Lithium php framework with backbone.

I want all my model id(s) and idAttribute(s) to be same as my database document id (i.e '_id'/mongoid)

Questions:

1. When I print the value of model.idAttribute, it is shown as just _id.
2. When I print model.get('idAttriubte'), it is undefined.
3. How do I ensure that the idAttribute is set as the same as the database id/mongoid?

Here is the model class:

window.app.IHoliday = Backbone.Model.extend({
    urlRoot: HOLIDAY_URL,
    idAttribute: '_id',
    id: '_id',
    // Default attributes for the holiday.
    defaults: {
    },

    initialize: function(props) {
    },      
});

Here is the view code, calling fetch on the model. The mongoid for the document is passed to this page as a hidden input (holiday_id).

console.log('Holiday URL:' + HOLIDAY_URL );
        var Holiday = new window.app.IHoliday({ _id: holiday_id });
        console.log('HOLIDAY before fetch: \n' + JSON.stringify(Holiday));
        Holiday.fetch(
                {
                    success: function(){
                        //alert('Holiday fetched:' + JSON.stringify(Holiday));
                        console.log('HOLIDAY Fetched: \n' + JSON.stringify(Holiday));
                        console.log('Holiday name:' + Holiday.get('holiday_name'));
                        console.log('Holiday id:' + Holiday.id);
                        console.log('Holiday idAttribute:' + Holiday.idAttribute);
                        console.log('Holiday idAttribute:' + Holiday.get('idAttribute'));
                    }
                });

The output from firebug console:

HOLIDAY before fetch:{"_id":"50bcaab24fbe3dfc1700000b"}
GET http://localhost:8080/li3/holidays/load/50bcaab24fbe3dfc1700000b 200 OK

HOLIDAY Fetched: 
{"_id":"50bcaab24fbe3dfc1700000b","holiday_name":"eeeeeeeeeeeeeeeee","description":"","star_rating":"3","holiday_type":"family","rooms":"1","adults":"2","child":"0","emails":""}

Holiday name:eeeeeeeeeeeeeeeee
Holiday id:50bcaab24fbe3dfc1700000b
Holiday idAttribute:_id
Holiday idAttribute:undefined

EDIT: The following worked...after commenting out the entry for id in the model class:

    window.app.IHoliday = Backbone.Model.extend({
    urlRoot: HOLIDAY_URL,
    //id: '_id',
    idAttribute: '_id',
    // Default attributes for the holiday.
    defaults: {
    },

    initialize: function(props) {
    },

Answer 1

idAttribute contains the name of the member of the class wich will be use as the id. So, if you use idAttribute: '_id', Backbone will use the member _id as the id of your class.

If you want to use the attribute holiday_id as the id of your class IHoliday, you may try :

window.app.IHoliday = Backbone.Model.extend({
    urlRoot: HOLIDAY_URL,
    idAttribute: 'holiday_id',
    // Default attributes for the holiday.
    defaults: {
    },

    initialize: function(props) {
    },      
});

var Holiday = new window.app.IHoliday({holiday_id : holiday_id });

Backbone will use the holiday_id attribute instead of the regular id attribute.