/**
* Initializes the DB connection component.
* This method will initialize the [[db]] property to make sure it refers to a valid DB connection.
* @return void
* @throws InvalidConfigException If [[db]] is invalid.
*/
public function init()
{
parent::init();
if (is_string($this->db)) {
$this->db = Instance::ensure($this->db, Connection::className());
}
}
