在一个UIViewController中，我如何判断是返回到下一个UIViewController，还是返回到上一个UIViewController

if let viewControllers = self.navigationController?.viewControllers {
    if viewControllers.count >= 2 && viewControllers[viewControllers.count - 2] is NextViewController {
        // 返回到下一个UIViewController
    } else {
        // 返回到上一个UIViewController
    }
}

if let presentingViewController = self.presentingViewController {
    if presentingViewController is NextViewController {
        // 返回到下一个UIViewController
    } else {
        // 返回到上一个UIViewController
    }
}

protocol PreviousViewControllerDelegate: class {
    func didReturnToPreviousViewController(from viewController: UIViewController)
}

weak var delegate: PreviousViewControllerDelegate?

func returnToPreviousViewController() {
    delegate?.didReturnToPreviousViewController(from: self)
}

extension PreviousViewController: PreviousViewControllerDelegate {
    func didReturnToPreviousViewController(from viewController: UIViewController) {
        if viewController is NextViewController {
            // 返回到下一个UIViewController
        } else {
            // 返回到上一个UIViewController
        }
    }
}