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Question

I am working to implement some SwiftUI content into my existing app. I currently have a UIViewController, which hosts a MTKView for camera preview.

I have created a new SwiftUI view, which is now my root view, as set in my SceneDelegate.swift file. The SwiftUI view loads at launch, as expected. Now, I would like to create a segue in which, when a user taps on a row in my List, it will segue, full-screen to my existing UIViewController. Here is how I'm calling that;

var body: some View {
    VStack {
        NavigationView {
            List(sessionTypes) { session in
                NavigationLink(destination: CameraControllerWrapper()) {
                    SessionRow(session: session)
                    .frame(height: 40.0)
                }
            }
        .navigationBarTitle(Text("Camera Types"))
        }
    }
}

For posterity, here is my CameraControllerWrapper UIViewControllerRepresentable;

struct CameraControllerWrapper: UIViewControllerRepresentable {
typealias UIViewControllerType = CameraController

   func makeUIViewController(context: UIViewControllerRepresentableContext<CameraControllerWrapper>) -> CameraControllerWrapper.UIViewControllerType {
    return CameraController()
   }

   func updateUIViewController(_ uiViewController: CameraControllerWrapper.UIViewControllerType, context: UIViewControllerRepresentableContext<CameraControllerWrapper>) {
    //
   }
}

While this "works," my app crashes as soon as the CameraController is called, as it seems any of my IBOutlets cannot be found. CameraController is a UIViewController built in the storyboard.

Answer 1

I managed to resolve this by realizing that I needed to instantiate the UIViewController from the Storyboard, and not in code (as I had built its layout in Storyboard, alongside some programatic elements). To use the above NavigationLink , I needed to adjust my UIViewControllerRepresentable as such;

struct CameraControllerWrapper: UIViewControllerRepresentable {
    typealias UIViewControllerType = CameraController

    func makeUIViewController(context: UIViewControllerRepresentableContext<CameraControllerWrapper>) -> CameraControllerWrapper.UIViewControllerType {

    let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
    let mainViewController: CameraController = mainStoryboard.instantiateViewController(withIdentifier: "CameraController") as! CameraController
      return mainViewController

    }

    func updateUIViewController(_ uiViewController: CameraControllerWrapper.UIViewControllerType, context: UIViewControllerRepresentableContext<CameraControllerWrapper>) {
        //
    }
}

Answer 2

A few potential optimizations for @ZbadhabitZ answer, for people who may be relatively new to Swift, starting with a brief example.

extension NotesVC : UIViewControllerRepresentable {

    func makeUIViewController(context: Context) -> NotesVC {
        let storyboard =  UIStoryboard(name: "Main", bundle: nil)
        let vc = storyboard.instantiateViewController(withIdentifier: "NotesVC") 
        return vc as! NotesVC
    }

    func updateUIViewController(_ vc: NotesVC, context: Context) {
        // your stuff here
    }
}

1. Consider adding Swift Protocols as extensions. It can be tidier and more flexible (including being able to adapt a class to a protocol by defining the protocol extension in a separate file entirely). For example, I recently tried out a 3rd party tab controller that required adapting my class to a protocol and the instructions entailed editing several files both added and my own and I was able to put 80% of it into a separate file as extensions and didn't have to muck up my code while experimenting with the new stuff, and it was easy to remove when I was done with it.

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2. Function arguments with the heavy typing are overkill; or confusing, at least.

   Apple Developer demo shows an example with PageViewController that shows all the extra typing isn't necessary:

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3. The original answer's code doesn't make use of Swift implied types. For example, rather

    let flag: Bool = false

   Instead write:

    let flag = false

   flag will be typed as Bool implicitly in that declaration. That is because false always implies Bool . Just as 1.0 always implies Double by default, and so on. The payoff gets even bigger when you start getting into longer class names.