Backbone initialize: function( options ) not working in V9

Question

I just upgrade a site I worked on from Backbone.js 0.5.3 to Backbone.js 0.9.2 When I did I get an undefined for my options parameter that I use in my models initialize method. What has changed from V.5 to V.9

initialize: function( options ) {enter code here }

Ok here is my model structure. Everything works fine in 0.5.3 but when I use 0.9.2 options no longer works.

this.myModel = Backbone.Model.extend({

        defaults: function() {
            return {
                maxDays: 7,
                index: 0

            };
        },

        initialize: function( options ) {

        }

})



this.model = new myModel();

In version 0.5.3 options will show all the attributes that were set in the defaults object. but in version 0.9.2 this no longer works it returns undefined. I can not post a link because of the client sensitivity.

Answer 1

The signature of initialize remains unchanged I believe from 0.5 to 0.9. However, you only get options passed in if you pass them to the constructor. Check out the annotated source for Backbone.Model. Whenever you instantiate a new model instance, the constructor does this:

this.initialize.apply(this, arguments);

So whatever you pass to the constructor gets passed unmodified to initialize. So look in your code for cases where you are instantiating a new model instance but not passing 2 arguments (attributes and options).

Based on your code sample, you now need to define initialize as taking 2 parameters: attributes and options and when creating your models, if you want to just pass options do:

var model = new Model(null, options);

or

var model = new Model({}, options);

I think the specific change that broke your code is the switch from calling initialize with explicit arguments in 0.5.3 to using apply and arguments in 0.9.3 like this:

    this.initialize.apply(this, arguments);

So in 0.9 you can get access to your defaults through this.attributes, but they won't come in as a function parameter unless they came in as a parameter to the constructor function.

var MyModel = Backbone.Model.extend({
    defaults: {x: 42, y: 43},
    initialize: function(attributes, options) {
        console.log(arguments, attributes, this.attributes);}
});
var m = new MyModel();

That will log [], undefined, Object since arguments is empty, attributes is undefined since nothing was passed to the constructor, but the defaults HAVE been set in this.attributes and are there for you to use.