class GoodsAction extends GoodsCommonAction{
//如果在这个action里面写构造函数
public function __construct(){
//do something
}
//那么其他的函数里面就不能用$this->assign('xx','xx')于 display等了
public function xxx(){
$this->assign('x','x');
//上面就要报Call to a member function assign() on a non-object

}
}