    /**
     * @class Ext.form.RadioGroup
     * @extends Ext.form.CheckboxGroup
     * <p>A {@link Ext.form.FieldContainer field container} which has a specialized layout for arranging
     * {@link Ext.form.field.Radio} controls into columns, and provides convenience {@link Ext.form.field.Field} methods
     * for {@link #getValue getting}, {@link #setValue setting}, and {@link #validate validating} the group
     * of radio buttons as a whole.</p>
     * <p><b>Validation:</b> Individual radio buttons themselves have no default validation behavior, but
     * sometimes you want to require a user to select one of a group of radios. RadioGroup
     * allows this by setting the config <tt>{@link #allowBlank}:false</tt>; when the user does not check at
     * one of the radio buttons, the entire group will be highlighted as invalid and the
     * {@link #blankText error message} will be displayed according to the {@link #msgTarget} config.</p>
     * <p><b>Layout:</b> The default layout for RadioGroup makes it easy to arrange the radio buttons into
     * columns; see the {@link #columns} and {@link #vertical} config documentation for details. You may also
     * use a completely different layout by setting the {@link #layout} to one of the other supported layout
     * types; for instance you may wish to use a custom arrangement of hbox and vbox containers. In that case
     * the Radio components at any depth will still be managed by the RadioGroup's validation.</p>
     * <p>Example usage:</p>
     * <pre><code>
    var myRadioGroup = new Ext.form.RadioGroup({
        id: 'myGroup',
        xtype: 'radiogroup',
        fieldLabel: 'Single Column',
        // Arrange radio buttons into three columns, distributed vertically
        columns: 3,
        vertical: true,
        items: [
            {boxLabel: 'Item 1', name: 'rb', inputValue: '1'},
            {boxLabel: 'Item 2', name: 'rb', inputValue: '2', checked: true},
            {boxLabel: 'Item 3', name: 'rb', inputValue: '3'}
            {boxLabel: 'Item 4', name: 'rb', inputValue: '4'}
            {boxLabel: 'Item 5', name: 'rb', inputValue: '5'}
            {boxLabel: 'Item 6', name: 'rb', inputValue: '6'}
        ]
    });
     * </code></pre>
     * @constructor
     * Creates a new RadioGroup
     * @param {Object} config Configuration options
     * @xtype radiogroup
     */
    Ext.define('Ext.form.RadioGroup', {
        extend: 'Ext.form.CheckboxGroup',
        alias: 'widget.radiogroup',

        /**
         * @cfg {Array} items An Array of {@link Ext.form.field.Radio Radio}s or Radio config objects
         * to arrange in the group.
         */
        /**
         * @cfg {Boolean} allowBlank True to allow every item in the group to be blank (defaults to true).
         * If allowBlank = false and no items are selected at validation time, {@link @blankText} will
         * be used as the error text.
         */
        allowBlank : true,
        /**
         * @cfg {String} blankText Error text to display if the {@link #allowBlank} validation fails
         * (defaults to 'You must select one item in this group')
         */
        blankText : 'You must select one item in this group',

        // private
        defaultType : 'radiofield',

        // private
        groupCls : Ext.baseCSSPrefix + 'form-radio-group',

        getBoxes: function() {
            return this.query('[isRadio]');
        }

    });