/** * 静态工厂方法,返还此类的唯一实例 */ public static function getInstance() { if (is_null(self::$_instance)) { self::$_instance = new ConcreteStateA(); } return self::$_instance; }
public static function getInstance() { // 静态工厂方法,返还此类的唯一实例 if (is_null(self::$_instance)) { self::$_instance = new ConcreteStateA(); } return self::$_instance; }