source: Dev/trunk/src/client/dijit/form/_RadioButtonMixin.js

define([
        "dojo/_base/array", // array.forEach
        "dojo/_base/declare", // declare
        "dojo/dom-attr", // domAttr.set
        "dojo/_base/lang", // lang.hitch
        "dojo/query", // query
        "../registry"    // registry.getEnclosingWidget
], function(array, declare, domAttr, lang, query, registry){

        // module:
        //              dijit/form/_RadioButtonMixin

        return declare("dijit.form._RadioButtonMixin", null, {
                // summary:
                //              Mixin to provide widget functionality for an HTML radio button

                // type: [private] String
                //              type attribute on `<input>` node.
                //              Users should not change this value.
                type: "radio",

                _getRelatedWidgets: function(){
                        // Private function needed to help iterate over all radio buttons in a group.
                        var ary = [];
                        query("input[type=radio]", this.focusNode.form || this.ownerDocument).forEach(// can't use name= since query doesn't support [] in the name
                                lang.hitch(this, function(inputNode){
                                        if(inputNode.name == this.name && inputNode.form == this.focusNode.form){
                                                var widget = registry.getEnclosingWidget(inputNode);
                                                if(widget){
                                                        ary.push(widget);
                                                }
                                        }
                                })
                        );
                        return ary;
                },

                _setCheckedAttr: function(/*Boolean*/ value){
                        // If I am being checked then have to deselect currently checked radio button
                        this.inherited(arguments);
                        if(!this._created){
                                return;
                        }
                        if(value){
                                array.forEach(this._getRelatedWidgets(), lang.hitch(this, function(widget){
                                        if(widget != this && widget.checked){
                                                widget.set('checked', false);
                                        }
                                }));
                        }
                },

                _getSubmitValue: function(/*String*/ value){
                        return value == null ? "on" : value;
                },

                _onClick: function(/*Event*/ e){
                        if(this.checked || this.disabled){ // nothing to do
                                e.stopPropagation();
                                e.preventDefault();
                                return false;
                        }
                        if(this.readOnly){ // ignored by some browsers so we have to resync the DOM elements with widget values
                                e.stopPropagation();
                                e.preventDefault();
                                array.forEach(this._getRelatedWidgets(), lang.hitch(this, function(widget){
                                        domAttr.set(this.focusNode || this.domNode, 'checked', widget.checked);
                                }));
                                return false;
                        }
                        return this.inherited(arguments);
                }
        });
});