Hide navigation bar without losing swipe back gesture in SwiftUI

This should work by just extending UINavigationController.

extension UINavigationController: UIGestureRecognizerDelegate {
    override open func viewDidLoad() {
        super.viewDidLoad()
        interactivePopGestureRecognizer?.delegate = self
    }

    public func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
        return viewControllers.count > 1
    }
}

It is even easier than what Nick Bellucci answered. Here is the simplest working solution:

extension UINavigationController {
    override open func viewDidLoad() {
        super.viewDidLoad()
        interactivePopGestureRecognizer?.delegate = nil
    }
}

When using the UINavigationController extension you might encounter a bug that blocks your navigation after you start swiping the screen and let it go without navigating back. Adding .navigationViewStyle(StackNavigationViewStyle()) to NavigationView does fix this issue.

If you need different view styles based on device, this extension helps:

extension View {
    public func currentDeviceNavigationViewStyle() -> AnyView {
        if UIDevice.current.userInterfaceIdiom == .pad {
            return AnyView(self.navigationViewStyle(DefaultNavigationViewStyle()))
        } else {
            return AnyView(self.navigationViewStyle(StackNavigationViewStyle()))
        }
    }
}

I looked around documentation and other sources about this issue and found nothing. There are only a few solutions, based on using UIKit and UIViewControllerRepresentable. I tried to combine solutions from this question and I saved swipe back gesture even while replacing back button with other view. The code is still dirty a little, but I think that is the start point to go further (totally hide navigation bar, for example). So, here is how ContentView looks like:

import SwiftUI

struct ContentView: View {

    var body: some View {

        SwipeBackNavController {

            SwipeBackNavigationLink(destination: DetailViewWithCustomBackButton()) {
                Text("Main view")
            }
            .navigationBarTitle("Standard SwiftUI nav view")


        }
        .edgesIgnoringSafeArea(.top)

    }

}

// MARK: detail view with custom back button
struct DetailViewWithCustomBackButton: View {

    @Environment(\.presentationMode) var presentationMode

    var body: some View {

        Text("detail")
            .navigationBarItems(leading: Button(action: {
                self.dismissView()
            }) {
                HStack {
                    Image(systemName: "return")
                    Text("Back")
                }
            })
        .navigationBarTitle("Detailed view")

    }

    private func dismissView() {
        presentationMode.wrappedValue.dismiss()
    }

}

Here is realization of SwipeBackNavController and SwipeBackNavigationLink which mimic NavigationView and NavigationLink. They are just wrappers for SwipeNavigationController's work. The last one is a subclass of UINavigationController, which can be customized for your needs:

import UIKit
import SwiftUI

struct SwipeBackNavController<Content: View>: UIViewControllerRepresentable {

    let content: Content

    public init(@ViewBuilder content: @escaping () -> Content) {
        self.content = content()
    }

    func makeUIViewController(context: Context) -> SwipeNavigationController {
        let hostingController = UIHostingController(rootView: content)
        let swipeBackNavController = SwipeNavigationController(rootViewController: hostingController)
        return swipeBackNavController
    }

    func updateUIViewController(_ pageViewController: SwipeNavigationController, context: Context) {

    }

}

struct SwipeBackNavigationLink<Destination: View, Label:View>: View {
    var destination: Destination
    var label: () -> Label

    public init(destination: Destination, @ViewBuilder label: @escaping () -> Label) {
        self.destination = destination
        self.label = label
    }

    var body: some View {
        Button(action: {
            guard let window = UIApplication.shared.windows.first else { return }
            guard let swipeBackNavController = window.rootViewController?.children.first as? SwipeNavigationController else { return }
            swipeBackNavController.pushSwipeBackView(DetailViewWithCustomBackButton())
        }, label: label)
    }
}

final class SwipeNavigationController: UINavigationController {

    // MARK: - Lifecycle

    override init(rootViewController: UIViewController) {
        super.init(rootViewController: rootViewController)
    }

    override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)

        delegate = self
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)

        delegate = self
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        // This needs to be in here, not in init
        interactivePopGestureRecognizer?.delegate = self

    }

    deinit {
        delegate = nil
        interactivePopGestureRecognizer?.delegate = nil
    }

    // MARK: - Overrides

    override func pushViewController(_ viewController: UIViewController, animated: Bool) {
        duringPushAnimation = true
        setNavigationBarHidden(true, animated: false)
        super.pushViewController(viewController, animated: animated)
    }

    var duringPushAnimation = false

    // MARK: - Custom Functions

    func pushSwipeBackView<Content>(_ content: Content) where Content: View {
        let hostingController = SwipeBackHostingController(rootView: content)
        self.delegate = hostingController
        self.pushViewController(hostingController, animated: true)
    }

}

// MARK: - UINavigationControllerDelegate

extension SwipeNavigationController: UINavigationControllerDelegate {

    func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool) {
        guard let swipeNavigationController = navigationController as? SwipeNavigationController else { return }

        swipeNavigationController.duringPushAnimation = false
    }

}

// MARK: - UIGestureRecognizerDelegate

extension SwipeNavigationController: UIGestureRecognizerDelegate {

    func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
        guard gestureRecognizer == interactivePopGestureRecognizer else {
            return true // default value
        }

        // Disable pop gesture in two situations:
        // 1) when the pop animation is in progress
        // 2) when user swipes quickly a couple of times and animations don't have time to be performed
        let result = viewControllers.count > 1 && duringPushAnimation == false
        return result
    }
}

// MARK: Hosting controller
class SwipeBackHostingController<Content: View>: UIHostingController<Content>, UINavigationControllerDelegate {
    func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool) {
        guard let swipeNavigationController = navigationController as? SwipeNavigationController else { return }
        swipeNavigationController.duringPushAnimation = false
    }

    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)

        guard let swipeNavigationController = navigationController as? SwipeNavigationController else { return }
        swipeNavigationController.delegate = nil
    }
}

This realization provides to save custom back button and swipe back gesture for now. I still don't like some moments, like how SwipeBackNavigationLink pushes view, so later I'll try to continue research.