Hosting Controller When Using iOS 14 @main

Question

I’m experimenting with a “pure” SwiftUI app. It doesn’t have a SceneDelegate so I’m unsure of where to put Hosting Controller stuff that I need for when it’ll be running on iOS.

Previously in the SceneDelegate I’d have code that would say something like:

let contentView = ContentView()
window.rootViewController = UIHostingController(rootView: contentView)

Now I just have an @main file with:

var body: some Scene {
    WindowGroup {
        ContentView()
    }
}

So where does the Hosting Controller stuff go (or how else can I access UIKit features that SwiftUI doesn’t have? (Specifically, I want to mess with the status bar, auto hiding the home indicator, and a few things about light/dark mode that SwiftUI’s preferredColorScheme doesn’t cover.)

Answer 1

Here is a possible approach (tested with Xcode 12 / iOS 14)... but if you intend to use UIKit features heavily it is better to use UIKit Life-Cycle, as it gives more flexibility to configure UIKit part.

struct ContentView: View {

    var body: some View {
      Text("Demo Root Controller access")
        .withHostingWindow { window in
            if let controller = window?.rootViewController {
                // .. do something with root view controller
            }
        }
    }
}

extension View {
    func withHostingWindow(_ callback: @escaping (UIWindow?) -> Void) -> some View {
        self.background(HostingWindowFinder(callback: callback))
    }
}

struct HostingWindowFinder: UIViewRepresentable {
    var callback: (UIWindow?) -> ()

    func makeUIView(context: Context) -> UIView {
        let view = UIView()
        DispatchQueue.main.async { [weak view] in
            self.callback(view?.window)
        }
        return view
    }

    func updateUIView(_ uiView: UIView, context: Context) {
    }
}

backup

Answer 2

I was facing the same problem. I played around with an alternative solution with zero set up, meaning it would work with SwiftUI App and Playgrounds (I even wrote a set of Playgrounds for documentation) - The package is called SwiftUIWindowBinder.

Example using WindowBinder... See docs for other usage, such as event view modifiers (like onTapGesture), or the convenience of WindowButton.

import SwiftUI
import SwiftUIWindowBinder

struct ContentView : View {
    /// Host window state (will be bound)
    @State var window: Window?

    var body: some View {
        // Create a WindowBinder and bind it to the state property `window`
        WindowBinder(window: $window) {
          
            Text("Hello")
                .padding()
                .onTapGesture {
                    guard let window = window else {
                        return
                    }

                    print(window.description)
                }
          
        }
    }
}

Only caveat of the package is you cannot use a host window to construct your view. I have a whole Playground page on this.