protected function db() { if (!isset($this->_dbs[$this->_dbName])) { if (!$this->_dbName) { throws(get_class($this) . ' 没有定义数据库,无法使用 Com_Dao', 'sql'); } $this->_dbs[$this->_dbName] = Com_Db::get($this->_dbName); } return $this->_dbs[$this->_dbName]; }