Fetch using promises

model.js

fetch: function()
{
    var deferred;
    var data = this.cache();

    if(data)
    {
        deferred = $.Deferred();
        deferred.resolve(data);
    }
    else
    {
        var ongoingAjaxFetch = this.get('ongoingAjaxFetch');
        if(ongoingAjaxFetch) return ongoingAjaxFetch;

        deferred = $.ajax({ ... });
        this.set('ongoingAjaxFetch', deferred);
    }

    $.when(deferred)
    .done(_.bind(this.fetchSuccess, this))
    .fail(_.bind(this.fetchFailure, this))
    .always(_.bind(this.fetchAlways, this));

    return deferred.promise();
}