内部带有导航控制器的PageViewController

import UIKit
import Firebase
import FirebaseAuth

class HomeViewController: UIPageViewController, UIPageViewControllerDataSource {
    let dropDownLauncher = DropDownLauncher()
        override func viewDidLoad() {
            super.viewDidLoad()
            self.dataSource = self
            if let firstViewController = viewControllerList.first{
                self.setViewControllers([firstViewController], direction: .forward, animated: true, completion: nil)
            }
            // setupView()
        }
    lazy var viewControllerList: [UINavigationController] = {
        let layout = UICollectionViewFlowLayout()
        let homeFeedController = HomeFeedController(collectionViewLayout: layout)
        let navController = UINavigationController(rootViewController: homeFeedController)
        let profileView = ProfileeViewController(collectionViewLayout: layout)
        let profileViewNavController = UINavigationController(rootViewController: profileView)
        let searchController = EventSearchController(collectionViewLayout: layout)
        let searchNavController = UINavigationController(rootViewController: searchController)

        return [navController,profileViewNavController,searchNavController]
    }()

    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UINavigationController) -> UINavigationController? {
        guard let vcIndex = viewControllerList.index(of: viewController) else{
            return nil
        }
        let previousIndex = vcIndex - 1
        guard previousIndex >= 0 else {
            return nil
        }
        guard viewControllerList.count > previousIndex else{
            return nil
        }
        return viewControllerList[previousIndex]
    }

    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UINavigationController) -> UINavigationController? {

        guard let vcIndex = viewControllerList.index(of: viewController) else{
            return nil
        }
        let nextIndex = vcIndex + 1
        guard viewControllerList.count != nextIndex else{
            return nil
        }
        guard viewControllerList.count > nextIndex else{
            return nil
        }

        return viewControllerList[nextIndex]
        }

}

有没有办法有效地做到这一点并消除这个错误? 因为我希望它们出现的顺序是确定的