An UIViewControllerRepresentable wrapper of UISplitViewController

UIKitSplitView.swift

/// UIKit製のUISplitViewController.
struct UIKitSplitView<Primary, Secondary>: UIViewControllerRepresentable where Primary : View, Secondary : View {
    
    typealias UIViewControllerType = UISplitViewController
    
    /// プライマリPaneのビューを生成するクロージャ
    var primary: () -> Primary
    
    /// セカンダリPaneのビューを生成するクロージャ
    var secondary: () -> Secondary
    
    var splitViewController: UISplitViewController
    
    var primaryHostingViewController: UIHostingController<Primary>
    
    var secondaryHostingViewController: UIHostingController<Secondary>
    
    init(@ViewBuilder primary: @escaping () -> Primary, @ViewBuilder secondary: @escaping () -> Secondary) {
        self.primary = primary
        self.secondary = secondary
        self.splitViewController = .init(style: .doubleColumn)
        self.primaryHostingViewController = .init(rootView: primary())
        self.secondaryHostingViewController = .init(rootView: secondary())
    }
    
    func makeUIViewController(context: Context) -> UISplitViewController {
        
        // Examples of customizations
        splitViewController.displayModeButtonVisibility = .never
        splitViewController.preferredSplitBehavior = .tile
        splitViewController.preferredDisplayMode = .oneBesideSecondary
        splitViewController.preferredPrimaryColumnWidth = 400
        splitViewController.minimumPrimaryColumnWidth = 400
        splitViewController.maximumPrimaryColumnWidth = 480
        splitViewController.delegate = context.coordinator
        
        let primaryNavigationController = UINavigationController(rootViewController: primaryHostingViewController)
        primaryNavigationController.navigationBar.prefersLargeTitles = true
        primaryNavigationController.isToolbarHidden = false
        primaryNavigationController.navigationItem.largeTitleDisplayMode = .automatic
        primaryHostingViewController.navigationItem.title = String(localized: "TitleYouWant")
        secondaryHostingViewController.navigationItem.largeTitleDisplayMode = .never
        secondaryHostingViewController.navigationItem.title = String(localized: "TitleYouWant")
                
        splitViewController.setViewController(primaryNavigationController, for: .primary)
        splitViewController.setViewController(secondaryHostingViewController, for: .secondary)
                
        return splitViewController
    }
    
    func updateUIViewController(_ uiViewController: UISplitViewController, context: Context) { }
    
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
    
    class Coordinator: NSObject, UISplitViewControllerDelegate {
        var owner: UIKitSplitView<Primary, Secondary>
        
        init(_ owner: UIKitSplitView<Primary, Secondary>) {
            self.owner = owner
            super.init()
            
            // Post notifications when your primary tableview changes its selection.
            NotificationCenter.default.addObserver(self, selector: #selector(showSecondary), name: .primarySelectionDidChangeNotification, object: nil)
        }
        
        func splitViewController(_ svc: UISplitViewController, topColumnForCollapsingToProposedTopColumn proposedTopColumn: UISplitViewController.Column) -> UISplitViewController.Column {
            return .primary
        }
        
        @objc func showSecondary(_ sender: Any?) {
            owner.secondaryHostingViewController.rootView = owner.secondary()
            owner.splitViewController.show(.secondary)
        }
        
    }
    
}