An example of how to create a lazy loaded paged view in SwiftUI

PageView.swift

import SwiftUI

/**
 A container view that manages navigation between pages of content.
 */
public struct PageView<Content: View, Item: Hashable> {
    
    public typealias ItemProvider = (Item) -> Item?
    public typealias ViewProvider = (Item) -> Content
    
    /// The style for transitions between pages.
    public enum TransitionStyle {
        case scroll
        case pageCurl
    }
    
    @Binding var selection: Item
    let style: TransitionStyle
    let axis: Axis
    let spacing: Int
    let prev: ItemProvider
    let next: ItemProvider
    @ViewBuilder let content: (Item) -> Content
    
    public init(selection: Binding<Item>, style: TransitionStyle = .scroll, axis: Axis = .horizontal, spacing: Int = 10, prev: @escaping ItemProvider, next: @escaping ItemProvider, @ViewBuilder content: @escaping ViewProvider) {
        _selection = selection
        self.style = style
        self.axis = axis
        self.spacing = spacing
        self.prev = prev
        self.next = next
        self.content = content
    }
}

extension PageView: UIViewControllerRepresentable {

    public typealias UIViewControllerType = UIPageViewController

    public func makeUIViewController(context: Context) -> UIPageViewController {
        let viewController = UIPageViewController(
            transitionStyle: style.uiPageViewController,
            navigationOrientation: axis.uiPageViewController,
            options: [.interPageSpacing: spacing]
        )
        viewController.delegate = context.coordinator
        viewController.dataSource = context.coordinator
        let initialView = ItemHostingController(item: selection, view: content(selection))
        viewController.setViewControllers([initialView], direction: .forward, animated: false)
        return viewController
    }
    
    public func updateUIViewController(_ uiViewController: UIPageViewController, context: Context) {
        let isAnimated = context.transaction.animation != nil
        goTo(selection, pageViewController: uiViewController, animated: isAnimated)
    }
    
    // MARK: - Navigation
    
    func goTo(_ item: Item, pageViewController: UIPageViewController, animated: Bool = true) {
        guard let currentViewController = pageViewController.viewControllers?.first as? ItemHostingController<Item> else {
            return
        }
        guard currentViewController.item != item else {
            return
        }
        let viewController = ItemHostingController(item: item, view: content(item))
        pageViewController.setViewControllers([viewController], direction: .forward, animated: animated)
    }
    
    // MARK: - Coordinator
    
    public func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
    
    public class Coordinator: NSObject, UIPageViewControllerDelegate, UIPageViewControllerDataSource {
        
        let pageView: PageView
        
        init(_ pageView: PageView) {
            self.pageView = pageView
        }
        
        // MARK: - Data Source
        
        public func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
            guard let viewController = viewController as? ItemHostingController<Item> else {
                return nil
            }
            if let prev = pageView.prev(viewController.item) {
                return makeView(prev)
            } else {
                return nil
            }
        }
        
        public func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
            guard let viewController = viewController as? ItemHostingController<Item> else {
                return nil
            }
            if let next = pageView.next(viewController.item) {
                print("Requesting item after \(viewController.item)")
                return makeView(next)
            } else {
                print("Nothing after \(viewController.item)")
                return nil
            }
        }
        
        // MARK: - Delegate
        
        public func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
            guard let viewController = pageViewController.viewControllers?.first as? ItemHostingController<Item> else {
                return
            }
            let item = viewController.item
            if pageView.selection != item {
                pageView.selection = item
            }
        }
        
        // MARK: - Helpers
        
        func makeView(_ item: Item) -> PageView.ItemHostingController<Item> {
            ItemHostingController(item: item, view: pageView.content(item))
        }
    }
    
    class ItemHostingController<Item>: UIHostingController<Content> {
        let item: Item
        
        init(item: Item, view: Content) {
            self.item = item
            super.init(rootView: view)
            self.view.backgroundColor = .clear
            self.view.isOpaque = false
        }
        
        @MainActor required dynamic init?(coder aDecoder: NSCoder) {
            fatalError("init(coder:) has not been implemented")
        }
    }
}

extension PageView.TransitionStyle {
    var uiPageViewController: UIPageViewController.TransitionStyle {
        switch self {
        case .scroll:
            return .scroll
        case .pageCurl:
            return .pageCurl
        }
    }
}

extension Axis {
    var uiPageViewController: UIPageViewController.NavigationOrientation {
        switch self {
        case .horizontal:
            return .horizontal
        case .vertical:
            return .vertical
        }
    }
}

struct PageView_Previews: PreviewProvider {
    
    static var previews: some View {
        CounterDemoView()
    }
    
    struct CounterDemoView: View {
        
        // Selection can be anything hashable (in practice, probably your model ID)
        @State private var selection: Int = 1
        
        var body: some View {
            VStack {
                PageView(selection: $selection, prev: prev, next: next) { item in
                    // This closure will be called each time a new page is needed
                    Text("Number \(item)")
                        .font(.largeTitle)
                        .frame(maxWidth: .infinity, maxHeight: .infinity)
                }
                .animation(.default, value: selection)
                
                Text("Current Number: \(selection)")
                
                // So we can test set setting the selection from SwiftUI
                Button {
                    if let next = next(selection) {
                        selection = next
                    }
                } label: {
                    Text("Next")
                }
            }
        }
        
        // Return the item that comes before
        func prev(_ item: Int) -> Int? {
            if item <= 0 {
                return nil
            } else {
                return item - 1
            }
        }
        
        // Return the item that comes after
        func next(_ item: Int) -> Int? {
            if item > 9 {
                return nil
            } else {
                return item + 1
            }
        }
    }
}