Pasted

import SwiftUI
import UIKit
 
class SomePageVC: UIViewController {
    let theLabel = UILabel()
    override func viewDidLoad() {
        super.viewDidLoad()
        theLabel.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(theLabel)
        NSLayoutConstraint.activate([
            theLabel.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            theLabel.centerYAnchor.constraint(equalTo: view.centerYAnchor),
        ])
        theLabel.font = .systemFont(ofSize: 60.0, weight: .light)
    }
}
class CustomPageViewController: UIPageViewController, UIPageViewControllerDelegate, UIPageViewControllerDataSource {
    
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
 
        guard let index = viewControllersList.firstIndex(of: viewController), index > 0 else {
            return nil
        }
        if let vc = viewControllersList[index - 1] as? SomePageVC {
            print("viewControllerBefore:", vc.theLabel.text)
        }
        return viewControllersList[index - 1]
        
    }
    
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        
        guard let index = viewControllersList.firstIndex(of: viewController), index < viewControllersList.count - 1 else {
            return nil
        }
        if let vc = viewControllersList[index + 1] as? SomePageVC {
            print("viewControllerAfter:", vc.theLabel.text)
        }
        return viewControllersList[index + 1]
 
    }
    
    lazy var viewControllersList: [UIViewController] = []
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        self.dataSource = self
        self.delegate = self
        
        let colors: [UIColor] = [
            .red, .green, .systemBlue, .yellow, .cyan, .lightGray,
        ]
        for i in 0..<6 {
            let vc = SomePageVC()
            vc.view.backgroundColor = colors[i % colors.count]
            vc.theLabel.text = "Page \(i)"
            viewControllersList.append(vc)
        }
        
        // if we have an odd number of "pages" we need to add a blank page at the end
        if viewControllersList.count % 2 == 1 {
            let vc = SomePageVC()
            vc.view.backgroundColor = .systemBackground
            vc.theLabel.text = "Blank"
            viewControllersList.append(vc)
        }
        
        if self.spineLocation == .mid {
            setViewControllers([viewControllersList[0], viewControllersList[1]], direction: .forward, animated: true)
        } else {
            setViewControllers([viewControllersList[0]], direction: .forward, animated: true)
        }
        
    }
    
    func pageViewController(_ pageViewController: UIPageViewController, spineLocationFor interfaceOrientation: UIInterfaceOrientation) -> UIPageViewController.SpineLocation {
 
        // safely unwrap optionals
        guard let curVC = pageViewController.viewControllers?.first, let idx = viewControllersList.firstIndex(of: curVC)
        else { fatalError("This should never happen!") }
        
        if interfaceOrientation.isLandscape {
            pageViewController.isDoubleSided = true
            let newIDX = (idx % 2 == 1) ? idx - 1 : idx
            setViewControllers([viewControllersList[newIDX], viewControllersList[newIDX + 1]], direction: .forward, animated: true, completion: nil)
        } else {
            pageViewController.isDoubleSided = false
            setViewControllers([viewControllersList[idx]], direction: .forward, animated: true, completion: nil)
        }
        
        return interfaceOrientation.isLandscape ? .mid : .min
        
    }
}
 
// 2. PageViewControllerRepresentable
struct MyViewControllerRepresentable: UIViewControllerRepresentable {
    
    func makeUIViewController(context: Context) -> CustomPageViewController {
        let pageViewController = CustomPageViewController(transitionStyle: .pageCurl, navigationOrientation: .horizontal)
        return pageViewController
    }
    
    func updateUIViewController(_ uiViewController: CustomPageViewController, context: Context) {
        // Update the UIPageViewController if needed
    }
    
}
 
struct TestView : View {
    var body: some View{
        VStack{
            MyViewControllerRepresentable()
        }
    }
}
 
#Preview {
    TestView()
}