经常有一些数据需要跟某个节点相关联，存放在Node中的m_pUserObject变量即可。

CCObject *m_pUserObject; ///< A user assigned CCObject

virtual CCObject* getUserObject();
virtual void setUserObject(CCObject *pUserObject);

lua中的使用：

存：

local itemPic = CCSprite:create(picName)
itemPic:setUserObject(CCString:create(itemId))


取：

local touchObj = tolua.cast(itemPic,"CCNode"):getUserObject()
local itemId = tolua.cast(touchObj,"CCString"):getCString()