Using override config in Ext.define class

override.js

/**
 * Using override config in Ext.define class (Ext JS 4.1)
 */
Ext.onReady(function () {

    Ext.define('MyWindow', {
        extend: 'Ext.window.Window',
        width: 300,
        height: 200,
        title: 'test',
        fbar: {
            items: [
                {
                    text:'OK',
                    handler: function(btn) {
                        this.up('window').onOk();
                    }
                }
            ]
        },

        onOk: function() {
            console.log('MyWindow!');
        }
    });

    Ext.define(null, {
        override: 'MyWindow',
        width: 300,
        title: 'Overrided',

        onOk: function () {
            this.callParent(arguments);
            console.log('overrided!!');
        }
    });
    Ext.create('MyWindow').show();

});