How to Navigating from SwiftUI View to UIKit UIViewController

Question

As of now, I have an application built entirely using UIKit. However, I wish to be able to start implementing some SwiftUI Views to replace some UIViewControllers.

I've been able to do this to navigate from the UIViewController to SwiftUI View on button tap:

    @IBAction func buttonTapped(_ sender: Any) {
        let newView = UIHostingController(rootView: SwiftUIView(viewObj: self.view, sb: self.storyboard, dismiss: self.dismiss) )
        view.window?.rootViewController = newView
        view.window?.makeKeyAndVisible()
    }

My question is, how would I transition from a single SwiftUI View to a UIViewController?(Since the rest of the application is in UIKit)? I've got a button in the SwiftUI View, to navigate back to the UIViewController on tap. I've tried:

1. Passing the view and storyboard objects to the SwiftUI View, then calling doing something similar to the code above to change the current view controller. However, when tried on the simulator nothing happens.
2. Using .present to show the SwiftUI View modally. This works and I can allow the SwiftUI View to .dismiss itself. However, this only works modally, and I hope to make this work properly (i.e change screen)

Here is my simple SwiftUI View:

struct SwiftUIView: View {
    var viewObj:UIView? // Perhaps use this for transition back?
    var sb:UIStoryboard?
    var dismiss: (() -> Void)?

    var body: some View {

        Button(action: {
            // Do something here to Transition
        }) {
            Text("This is a SwiftUI view.")
        }
    }
}

I'm having trouble understanding how to properly integrate SwiftUI into UIKit NOT the other way around, and I'm not sure if UIViewControllerRepresentable is the answer to this. Any solution to this, alternatives or helpful knowledge is very much appreciated. Thanks again!

Answer 1

Ciao,

I tried to follow your approach by using closure callbacks.

struct SwiftUIView: View {
    var dismiss: (() -> Void)?
    var present: (()->Void)?

    var body: some View {
        VStack(spacing: 20) {
            Button(action: {
                self.dismiss?()
            }) {
                Text("Dismiss me")
            }
            Button(action: {
                self.present?()
            }) {
                Text("Present some UIViewController")
            }
        }
    }
}

When you present your UIHostingController, you want to implement the 2 closure callbacks:

@IBAction func buttonTapped(_ sender: Any) {
    let hostingController = UIHostingController(rootView: SwiftUIView())
    hostingController.rootView.dismiss = {
        hostingController.dismiss(animated: true, completion: nil)
    }
    hostingController.rootView.present = {
        let destination = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(identifier: "VC_TO_PRESENT")
        hostingController.present(destination, animated: true, completion: nil)
    }

    present(hostingController, animated: true, completion: nil)
}

Answer 2

You can do the same, only in mirror order, like following (scratchy) ...

    Button(action: {
        if let vc = self.sb?.instantiateViewController(withIdentifier: "some_identifier") {
            self.viewObj?.window?.rootViewController = vc
            // or via present as alternate
            // self.viewObj?.window?.rootViewController.present(vc, animated: true, completion: nil)
        }
    }) {

Answer 3

you can change the presentation style and transition style to present the controller full screen

let vc = UIHostingController(rootView: LoginView())
vc.modalPresentationStyle = .fullScreen
vc.modalTransitionStyle = .crossDissolve
self.present(vc, animated: true)