SwiftUI : how to access UINavigationController from NavigationView

Question

I am developing an app using SwiftUI. The app is based around a NavigationView.

I am using a third-party framework that provides UIKit components and the framework has not been updated to support SwiftUI yet.

One framework method is expecting a parameter of type UINavigationController

How can I supply this framework the NavigationController created by SwiftUI ? Or how can I create a UINavigationController that will replace SwiftUI's default ?

I read https://developer.apple.com/tutorials/swiftui/interfacing-with-uikit and https://sarunw.com/posts/uikit-in-swiftui but these seems to address another question : they explain how to use UIKit components in a SwiftUI app. My problem is the other way around, I want to use SwiftUI App and access underlying NavigationController object.

[UPDATE] The code implementing my solution is available from this workshop : https://amplify-ios-workshop.go-aws.com/30_add_authentication/20_client_code.html#loginviewcontroller-swift

Answer 1

Thanks to Yonat's explanation I understood how to do this and here is my solution, hoping it will help others.

Part 1 : The UI View Controller that will be used from Swift UI. It calls a third-party authentication library, passing the UINavigationControler as parameter. The UINavigationController is an empty view, just there to allow the third-party authentication library to have a Navigation Controller to pop up the Login Screen.

struct LoginViewController: UIViewControllerRepresentable {

    let navController =  UINavigationController()


    func makeUIViewController(context: Context) -> UINavigationController {
        navController.setNavigationBarHidden(true, animated: false)
        let viewController = UIViewController()
        navController.addChild(viewController)
        return navController
    }

    func updateUIViewController(_ pageViewController: UINavigationController, context: Context) {
    }

    func makeCoordinator() -> Coordinator {
        return Coordinator(self)
    }

    class Coordinator: NSObject {
        var parent: LoginViewController

        init(_ loginViewController: LoginViewController) {
            self.parent = loginViewController
        }
    }

    func authenticate() {
        let app = UIApplication.shared.delegate as! AppDelegate
        let userData = app.userData

        userData.authenticateWithDropinUI(navigationController: navController)
    }

}

Part 2 : The Swift UI View is displaying the (empty) UINavigationControler and overlays a SwiftUI view on top of it.

import SwiftUI

struct LandingView: View {
    @ObservedObject public var user : UserData

    var body: some View {

        let loginView = LoginViewController()

        return VStack {

            // .wrappedValue is used to extract the Bool from Binding<Bool> type
            if (!$user.isSignedIn.wrappedValue) {

                ZStack {
                    loginView
                    // build your welcome view here 
                    Button(action: { loginView.authenticate() } ) {
                        UserBadge().scaleEffect(0.5)
                    }
                }

            } else {

                // my main app view 
                // ...
            }
        }
    }
}

Answer 2

I don't think you can do that right now. Looking at the view debugger for NavigationView I get the image below.

So it seems to you will have to go the other way around:
Start with a UINavigationController, and wrap the SwiftUI view(s) in UIHostingController.