SwiftUI NavigationView example for iPad

navigation.swift

import SwiftUI

var hostingController: UIViewController?

func getUISplitViewController() -> UISplitViewController {
    if hostingController?.children.count == 0 {
        fatalError()
    }
    guard let split = hostingController?.children[0] as? UISplitViewController else {
        fatalError()
    }
    return split
}

func isCollapsed() -> Bool {
    getUISplitViewController().isCollapsed
}

func isAllVisible() -> Bool {
    getUISplitViewController().displayMode == .allVisible
}

func showPrimary() {
    let split = getUISplitViewController()
    if split.isCollapsed {
        return
    }
    UIView.animate(withDuration: 0.3, animations: {
        split.preferredDisplayMode = .primaryOverlay
    }) { _ in
        split.preferredDisplayMode = .automatic
    }
}

func hidePrimary() {
    let split = getUISplitViewController()
    if split.isCollapsed || split.displayMode == .allVisible {
        return
    }
    DispatchQueue.main.async {
        split.preferredDisplayMode = .primaryHidden
    }
    DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
        split.preferredDisplayMode = .automatic
    }
}

// =====

struct DetailView: View {
    var item: Int
    var body: some View {
        VStack {
            Text("Item \(self.item)")
            if !isCollapsed() && !isAllVisible() {
                Button(action: showPrimary) {
                    Image(systemName: "sidebar.left")
                }
            }
        }
        .onAppear {
            hidePrimary()
        }
    }
}

struct ContentView: View {
    var body: some View {
        NavigationView {
            List {
                ForEach(1...100, id: \.self) { i in
                    NavigationLink(destination: DetailView(item: i)) {
                        Text("Item \(i)")
                    }
                }
            }
            VStack {
                Button(action: showPrimary) {
                    Image(systemName: "sidebar.left")
                }
                Text("or swipe")
            }
        }
    }
}

import PlaygroundSupport
hostingController = UIHostingController(rootView: ContentView())
PlaygroundPage.current.setLiveView(hostingController!)