Using Uisheetpresentationcontroller in Swiftui

Using UISheetPresentationController in SwiftUI

If you want the Image Picker

import SwiftUI
///Sample usage
@available(iOS 15.0, macCatalyst 15.0,*)
struct ImagePickerParentView: View {
    @State var isPresented = false
    @State var selectedImage: UIImage? = nil
    var body: some View {
        print("ImagePickerParentView :: \(#function) :: isPresented == \(isPresented)")
        
        return VStack{
            if selectedImage != nil{
                Image(uiImage: selectedImage!)
                    .resizable()
                    .frame(width: 100, height: 100)
            }
            Button("present image picker", action: {
                isPresented.toggle()
            }).imagePicker(isPresented: $isPresented, uiImage: $selectedImage, detents: [.medium()], largestUndimmedDetentIdentifier: .large)
            
        }
    }
}
@available(iOS 15.0, macCatalyst 15.0,*)
extension View {
    func imagePicker(isPresented: Binding<Bool>, uiImage: Binding<UIImage?>, detents : [UISheetPresentationController.Detent] = [.medium(), .large()], largestUndimmedDetentIdentifier: UISheetPresentationController.Detent.Identifier? = .medium, prefersScrollingExpandsWhenScrolledToEdge: Bool = false, prefersEdgeAttachedInCompactHeight: Bool = true, prefersGrabberVisible: Bool = false,  preferredCornerRadius: CGFloat? = nil)-> some View {
        print("\(#function) :: isPresented == \(isPresented)")
        return modifier(ImagePickerViewModifier(isPresented: isPresented, uiImage: uiImage, detents : detents, largestUndimmedDetentIdentifier: largestUndimmedDetentIdentifier, prefersScrollingExpandsWhenScrolledToEdge: prefersScrollingExpandsWhenScrolledToEdge, prefersEdgeAttachedInCompactHeight: prefersEdgeAttachedInCompactHeight, prefersGrabberVisible: prefersGrabberVisible, preferredCornerRadius: preferredCornerRadius))
    }
}
@available(iOS 15.0, macCatalyst 15.0,*)
struct ImagePickerViewModifier: ViewModifier {
    
    @Binding var isPresented: Bool
    @Binding var uiImage: UIImage?
    let detents : [UISheetPresentationController.Detent]
    let largestUndimmedDetentIdentifier: UISheetPresentationController.Detent.Identifier?
    let prefersScrollingExpandsWhenScrolledToEdge: Bool
    let prefersEdgeAttachedInCompactHeight: Bool
    let prefersGrabberVisible: Bool
    let preferredCornerRadius: CGFloat?
    
    func body(content: Content) -> some View {
        print("ImagePickerViewModifier :: \(#function) :: isPresented == \(isPresented)")
        return content.overlay(
            AdaptiveImagePicker_UI(isPresented: $isPresented, uiImage: $uiImage, detents: detents, largestUndimmedDetentIdentifier: largestUndimmedDetentIdentifier, prefersScrollingExpandsWhenScrolledToEdge: prefersScrollingExpandsWhenScrolledToEdge, prefersEdgeAttachedInCompactHeight: prefersEdgeAttachedInCompactHeight, prefersGrabberVisible: prefersGrabberVisible, preferredCornerRadius: preferredCornerRadius).frame(width: 0, height: 0)
            
        )
        
            .onChange(of: isPresented, perform: { value in
                print("AdaptiveSheet :: onChange :: isPresented == \(value)")
            })
        
        //}
    }
}

@available(iOS 15.0, macCatalyst 15.0,*)
struct AdaptiveImagePicker_UI: UIViewControllerRepresentable {
    @Binding var isPresented: Bool
    @Binding var uiImage: UIImage?
    var detents : [UISheetPresentationController.Detent] = [.medium(), .large()]
    var largestUndimmedDetentIdentifier: UISheetPresentationController.Detent.Identifier? = .medium
    var prefersScrollingExpandsWhenScrolledToEdge: Bool = false
    var prefersEdgeAttachedInCompactHeight: Bool = true
    var prefersGrabberVisible: Bool = false
    var preferredCornerRadius: CGFloat?
    
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
    func makeUIViewController(context: Context) -> AdaptiveImagePickerViewController {
        print("CustomSheet_UI :: \(#function) :: isPresented == \(isPresented)")
        let vc = AdaptiveImagePickerViewController(coordinator: context.coordinator, detents : detents, largestUndimmedDetentIdentifier: largestUndimmedDetentIdentifier, prefersScrollingExpandsWhenScrolledToEdge:  prefersScrollingExpandsWhenScrolledToEdge, prefersEdgeAttachedInCompactHeight: prefersEdgeAttachedInCompactHeight, prefersGrabberVisible: prefersGrabberVisible, preferredCornerRadius: preferredCornerRadius)
        return vc
    }
    
    func updateUIViewController(_ uiViewController: AdaptiveImagePickerViewController, context: Context) {
        print("CustomSheet_UI :: \(#function) :: isPresented == \(isPresented)")
        print("CustomSheet_UI :: \(#function) :: context.coordinator.parent.isPresented == \(context.coordinator.parent.isPresented)")
        if isPresented {
            uiViewController.presentImagePicker()
        }else{
            uiViewController.dismissModalView()
        }
    }
    class Coordinator: NSObject, UIAdaptivePresentationControllerDelegate, UIImagePickerControllerDelegate, UINavigationControllerDelegate {
        var parent: AdaptiveImagePicker_UI
        var isPresented: Bool = false
        init(_ parent: AdaptiveImagePicker_UI) {
            print("CustomSheet_UI :: \(#function) :: parent.isPresented == \(parent.isPresented)")
            
            self.parent = parent
        }
        //Adjust the variable when the user dismisses with a swipe
        func presentationControllerDidDismiss(_ presentationController: UIPresentationController) {
            print("CustomSheet_UI.Coordinator :: \(#function) :: parent.isPresented == \(parent.isPresented)")
            if parent.isPresented{
                parent.isPresented = false
            }
        }
        //Adjust the variable when the user cancels
        func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
            if parent.isPresented{
                parent.isPresented = false
            }
        }
        //Get access to the selected image
        func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey: Any]) {
            
            if let image = info[.originalImage] as? UIImage {
                parent.uiImage = image
                parent.isPresented = false
            }
        }
        
    }
}

@available(iOS 15.0, macCatalyst 15.0,*)
class AdaptiveImagePickerViewController: UIViewController {
    var coordinator: AdaptiveImagePicker_UI.Coordinator
    let detents : [UISheetPresentationController.Detent]
    let largestUndimmedDetentIdentifier: UISheetPresentationController.Detent.Identifier?
    let prefersScrollingExpandsWhenScrolledToEdge: Bool
    let prefersEdgeAttachedInCompactHeight: Bool
    let prefersGrabberVisible: Bool
    let preferredCornerRadius: CGFloat?
    private var isLandscape: Bool = UIDevice.current.orientation.isLandscape
    init(coordinator: AdaptiveImagePicker_UI.Coordinator, detents : [UISheetPresentationController.Detent] = [.medium(), .large()], largestUndimmedDetentIdentifier: UISheetPresentationController.Detent.Identifier? = .medium, prefersScrollingExpandsWhenScrolledToEdge: Bool = false, prefersEdgeAttachedInCompactHeight: Bool = true, prefersGrabberVisible: Bool, preferredCornerRadius: CGFloat?) {
        print("AdaptiveImagePickerViewController :: \(#function) :: isPresented == \(coordinator.parent.isPresented)")
        self.coordinator = coordinator
        self.detents = detents
        self.largestUndimmedDetentIdentifier = largestUndimmedDetentIdentifier
        self.prefersEdgeAttachedInCompactHeight = prefersEdgeAttachedInCompactHeight
        self.prefersScrollingExpandsWhenScrolledToEdge = prefersScrollingExpandsWhenScrolledToEdge
        self.prefersGrabberVisible = prefersGrabberVisible
        self.preferredCornerRadius = preferredCornerRadius
        super.init(nibName: nil, bundle: .main)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    func dismissModalView(){
        print("AdaptiveImagePickerViewController :: \(#function) :: isPresented == \(coordinator.parent.isPresented)")
        
        dismiss(animated: true, completion: nil)
    }
    
    //This is mostly code from the Apple sample
    //https://developer.apple.com/documentation/uikit/uiviewcontroller/customize_and_resize_sheets_in_uikit
    func presentImagePicker(){
        guard presentedViewController == nil else {
            dismiss(animated: true, completion: {
                self.presentImagePicker()
            })
            return
        }
        
        let imagePicker = UIImagePickerController()
        imagePicker.delegate = coordinator
        imagePicker.modalPresentationStyle = .popover
        //Added the presentation controller delegate to detect if the user swipes to dismiss
        imagePicker.presentationController?.delegate = coordinator as UIAdaptivePresentationControllerDelegate
        
        if let hostPopover = imagePicker.popoverPresentationController {
            hostPopover.sourceView = super.view
            
            let sheet = hostPopover.adaptiveSheetPresentationController
            //As of 13 Beta 4 if .medium() is the only detent in landscape error occurs
            sheet.detents = (isLandscape ? [.large()] : detents)
            sheet.largestUndimmedDetentIdentifier =
            largestUndimmedDetentIdentifier
            sheet.prefersScrollingExpandsWhenScrolledToEdge =
            prefersScrollingExpandsWhenScrolledToEdge
            sheet.prefersEdgeAttachedInCompactHeight =
            prefersEdgeAttachedInCompactHeight
            sheet.widthFollowsPreferredContentSizeWhenEdgeAttached = true
            sheet.prefersGrabberVisible = prefersGrabberVisible
            sheet.preferredCornerRadius = preferredCornerRadius
        }
        
        present(imagePicker, animated: true, completion: nil)
    }
    
    /// To compensate for l orientation
    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
        
        if UIDevice.current.orientation.isLandscape {
            isLandscape = true
            self.presentedViewController?.popoverPresentationController?.adaptiveSheetPresentationController.detents = [.large()]
        } else {
            isLandscape = false
            self.presentedViewController?.popoverPresentationController?.adaptiveSheetPresentationController.detents = detents
        }
        super.viewWillTransition(to: size, with: coordinator)
        
    }
}

@available(iOS 15.0, macCatalyst 15.0,*)
struct ImagePickerParentView_Previews: PreviewProvider {
    static var previews: some View {
        ImagePickerParentView()
    }
}

If you want one that takes any SwiftUI View it only needs a few changes.

//This is the sample usage
@available(iOS 15.0, macCatalyst 15.0,*)
struct CustomSheetParentView: View {
    @State var isPresented = false
    var body: some View {
        print("CustomSheetParentView :: \(#function) :: isPresented == \(isPresented)")
        
        return VStack{
            Button("present sheet", action: {
                isPresented.toggle()
            }).adaptiveSheet(isPresented: $isPresented, detents: [.medium()], largestUndimmedDetentIdentifier: .medium,  disableSwipeToDismiss: false){
                Rectangle()
                    .frame(maxWidth: .infinity, maxHeight: 100, alignment: .center)
                    .foregroundColor(.clear)
                
                    .border(Color.blue, width: 3)
                    .overlay(
                        LazyVStack{
                            Text("Hello, World!")
                            Button("dismiss", action: {
                                print("dismiss button :: isPresented == \(isPresented)")
                                isPresented = false
                            })
                            CustomSheetParentView()
                        }
                            .frame(maxWidth: .infinity, maxHeight: .infinity)
                            .onTapGesture {
                                print("onTap :: isPresented == \(isPresented)")
                                
                                isPresented.toggle()
                            }
                    )
                
                    .background(Color(UIColor.systemBackground))
            }
            
        }
    }
}
@available(iOS 15.0, macCatalyst 15.0,*)
struct CustomSheetView_Previews: PreviewProvider {
    static var previews: some View {
        CustomSheetParentView()
    }
}

//EVERYTHING from here down is Reusable and can be pasted into a project and then use `.adaptiveSheet` just like `.sheet`
@available(iOS 15.0, macCatalyst 15.0,*)
extension View {
    func adaptiveSheet<T: View>(isPresented: Binding<Bool>, detents : [UISheetPresentationController.Detent] = [.medium(), .large()], largestUndimmedDetentIdentifier: UISheetPresentationController.Detent.Identifier? = .medium, prefersScrollingExpandsWhenScrolledToEdge: Bool = false, prefersEdgeAttachedInCompactHeight: Bool = true, prefersGrabberVisible: Bool = false, disableSwipeToDismiss: Bool = false, preferredCornerRadius: CGFloat? = nil, @ViewBuilder content: @escaping () -> T)-> some View {
        print("\(#function) :: isPresented == \(isPresented)")
        return modifier(AdaptiveSheet<T>(isPresented: isPresented, detents : detents, largestUndimmedDetentIdentifier: largestUndimmedDetentIdentifier, prefersScrollingExpandsWhenScrolledToEdge: prefersScrollingExpandsWhenScrolledToEdge, prefersEdgeAttachedInCompactHeight: prefersEdgeAttachedInCompactHeight, prefersGrabberVisible: prefersGrabberVisible, disableSwipeToDismiss: disableSwipeToDismiss, preferredCornerRadius: preferredCornerRadius, sheetContent: content))
    }
}
@available(iOS 15.0, macCatalyst 15.0,*)
struct AdaptiveSheet<T: View>: ViewModifier {
    
    @Binding var isPresented: Bool
    let detents : [UISheetPresentationController.Detent]
    let largestUndimmedDetentIdentifier: UISheetPresentationController.Detent.Identifier?
    let prefersScrollingExpandsWhenScrolledToEdge: Bool
    let prefersEdgeAttachedInCompactHeight: Bool
    let prefersGrabberVisible: Bool
    let disableSwipeToDismiss: Bool
    let preferredCornerRadius: CGFloat?
    @ViewBuilder let sheetContent: T
    
    func body(content: Content) -> some View {
        print("AdaptiveSheet :: \(#function) :: isPresented == \(isPresented)")
        return content.overlay(
            CustomSheet_UI(isPresented: $isPresented, detents: detents, largestUndimmedDetentIdentifier: largestUndimmedDetentIdentifier, prefersScrollingExpandsWhenScrolledToEdge: prefersScrollingExpandsWhenScrolledToEdge, prefersEdgeAttachedInCompactHeight: prefersEdgeAttachedInCompactHeight, prefersGrabberVisible: prefersGrabberVisible, disableSwipeToDismiss: disableSwipeToDismiss,preferredCornerRadius: preferredCornerRadius, content: {sheetContent}).frame(width: 0, height: 0)
            
        )
        
            .onChange(of: isPresented, perform: { value in
                print("AdaptiveSheet :: onChange :: isPresented == \(value)")
            })
        
        //}
    }
}

@available(iOS 15.0, macCatalyst 15.0,*)
struct CustomSheet_UI<T: View>: UIViewControllerRepresentable {
    @Binding var isPresented: Bool
    var detents : [UISheetPresentationController.Detent] = [.medium(), .large()]
    var largestUndimmedDetentIdentifier: UISheetPresentationController.Detent.Identifier? = .medium
    var prefersScrollingExpandsWhenScrolledToEdge: Bool = false
    var prefersEdgeAttachedInCompactHeight: Bool = true
    var prefersGrabberVisible: Bool = false
    var disableSwipeToDismiss: Bool = false
    var preferredCornerRadius: CGFloat?
    @ViewBuilder let content: T
    
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
    func makeUIViewController(context: Context) -> CustomSheetViewController<T> {
        print("CustomSheet_UI :: \(#function) :: isPresented == \(isPresented)")
        let vc = CustomSheetViewController(coordinator: context.coordinator, detents : detents, largestUndimmedDetentIdentifier: largestUndimmedDetentIdentifier, prefersScrollingExpandsWhenScrolledToEdge:  prefersScrollingExpandsWhenScrolledToEdge, prefersEdgeAttachedInCompactHeight: prefersEdgeAttachedInCompactHeight, prefersGrabberVisible: prefersGrabberVisible, disableSwipeToDismiss: disableSwipeToDismiss, preferredCornerRadius: preferredCornerRadius, content: {content})
        return vc
    }
    
    func updateUIViewController(_ uiViewController: CustomSheetViewController<T>, context: Context) {
        print("CustomSheet_UI :: \(#function) :: isPresented == \(isPresented)")
        print("CustomSheet_UI :: \(#function) :: context.coordinator.parent.isPresented == \(context.coordinator.parent.isPresented)")
        if isPresented {
            uiViewController.presentModalView()
        }else{
            uiViewController.dismissModalView()
        }
    }
    class Coordinator: NSObject, UIAdaptivePresentationControllerDelegate {
        var parent: CustomSheet_UI
        var isPresented: Bool = false
        init(_ parent: CustomSheet_UI) {
            print("CustomSheet_UI :: \(#function) :: parent.isPresented == \(parent.isPresented)")
            
            self.parent = parent
        }
        //Adjust the variable when the user dismisses with a swipe
        func presentationControllerDidDismiss(_ presentationController: UIPresentationController) {
            print("CustomSheet_UI.Coordinator :: \(#function) :: parent.isPresented == \(parent.isPresented)")
            if parent.isPresented{
                parent.isPresented = false
            }
        }
        
    }
}

@available(iOS 15.0, macCatalyst 15.0,*)
class CustomSheetViewController<Content: View>: UIViewController {
    let content: Content
    var coordinator: CustomSheet_UI<Content>.Coordinator
    let detents : [UISheetPresentationController.Detent]
    let largestUndimmedDetentIdentifier: UISheetPresentationController.Detent.Identifier?
    let prefersScrollingExpandsWhenScrolledToEdge: Bool
    let prefersEdgeAttachedInCompactHeight: Bool
    let prefersGrabberVisible: Bool
    let disableSwipeToDismiss: Bool
    let preferredCornerRadius: CGFloat?
    private var isLandscape: Bool = UIDevice.current.orientation.isLandscape
    init(coordinator: CustomSheet_UI<Content>.Coordinator, detents : [UISheetPresentationController.Detent] = [.medium(), .large()], largestUndimmedDetentIdentifier: UISheetPresentationController.Detent.Identifier? = .medium, prefersScrollingExpandsWhenScrolledToEdge: Bool = false, prefersEdgeAttachedInCompactHeight: Bool = true, prefersGrabberVisible: Bool, disableSwipeToDismiss: Bool, preferredCornerRadius: CGFloat?, @ViewBuilder content: @escaping () -> Content) {
        print("CustomSheetViewController :: \(#function) :: isPresented == \(coordinator.parent.isPresented)")
        self.content = content()
        self.coordinator = coordinator
        self.detents = detents
        self.largestUndimmedDetentIdentifier = largestUndimmedDetentIdentifier
        self.prefersEdgeAttachedInCompactHeight = prefersEdgeAttachedInCompactHeight
        self.prefersScrollingExpandsWhenScrolledToEdge = prefersScrollingExpandsWhenScrolledToEdge
        self.prefersGrabberVisible = prefersGrabberVisible
        self.disableSwipeToDismiss = disableSwipeToDismiss
        self.preferredCornerRadius = preferredCornerRadius
        super.init(nibName: nil, bundle: .main)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    func dismissModalView(){
        print("CustomSheetViewController :: \(#function) :: isPresented == \(coordinator.parent.isPresented)")
        
        dismiss(animated: true, completion: nil)
    }
    func presentModalView(){
        print("CustomSheetViewController :: \(#function) :: isPresented == \(coordinator.parent.isPresented)")
        
        let hostingController = UIHostingController(rootView: content)
        //allows background color to be decided by SwiftUI content.
        // Incase you want to use a Material that gives transparency
        hostingController.view.backgroundColor = nil
        hostingController.modalPresentationStyle = .popover
        hostingController.presentationController?.delegate = coordinator as UIAdaptivePresentationControllerDelegate
        hostingController.modalTransitionStyle = .coverVertical
        hostingController.isModalInPresentation = disableSwipeToDismiss
        
        if let hostPopover = hostingController.popoverPresentationController {
            hostPopover.sourceView = super.view
            
            let sheet = hostPopover.adaptiveSheetPresentationController
            //As of 13 Beta 4 if .medium() is the only detent in landscape error occurs
            sheet.detents = (isLandscape ? [.large()] : detents)
            sheet.largestUndimmedDetentIdentifier =
            largestUndimmedDetentIdentifier
            sheet.prefersScrollingExpandsWhenScrolledToEdge =
            prefersScrollingExpandsWhenScrolledToEdge
            sheet.prefersEdgeAttachedInCompactHeight =
            prefersEdgeAttachedInCompactHeight
            sheet.widthFollowsPreferredContentSizeWhenEdgeAttached = true
            sheet.prefersGrabberVisible = prefersGrabberVisible
            sheet.preferredCornerRadius = preferredCornerRadius
        }
        if presentedViewController == nil{
            present(hostingController, animated: true, completion: nil)
        }
    }
    /// To compensate for l orientation
    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
        
        if UIDevice.current.orientation.isLandscape {
            isLandscape = true
            self.presentedViewController?.popoverPresentationController?.adaptiveSheetPresentationController.detents = [.large()]
        } else {
            isLandscape = false
            self.presentedViewController?.popoverPresentationController?.adaptiveSheetPresentationController.detents = detents
        }
        super.viewWillTransition(to: size, with: coordinator)
        
    }
}

How to present a modal view controller like with UIKit's UIViewControllerTransitioningDelegate?

Well there is no built-in such flexibility say with standard .sheet, but it can be implemented custom very fast.

Here is simple demo (Xcode 13.3 / iOS 15.4)

demo

Main part:

struct ElementsList: View {
// ...
        ModalView(isPresented: $isModal) {
            List(elements, id: \.self) {

struct ModalView<V: View>: View {
    @Binding var isPresented: Bool
// ...
        ZStack {
            content()
            ZStack {
                VStack {
                    if isPresented {
                        Color.black.opacity(0.8)
                            .transition(.opacity)
                    }
                }.animation(.easeInOut(duration: 0.25), value: isPresented)

Complete test code in project is here

Set UIWindowScene.PresentationStyle on Scene?

I've reached out to Apple via a TSI about this particular issue. As of the current release of SwiftUI, this isn't possible. They recommend I use the .sheet modifier instead and drop the split window capability. Otherwise, I can create a UISceneDelegate and use UIKit APIs directly:

let options = UIWindowScene.ActivationRequestOptions()
options.preferredPresentationStyle = .prominent
let userActivity = NSUserActivity(activityType: SecondSceneDelegate.sceneUserActivityType)
userActivity.targetContentIdentifier = SecondSceneDelegate.sceneUserActivityType

UIApplication.shared.requestSceneSessionActivation(nil,
    userActivity: userActivity,
    options: options,
    errorHandler: nil)

SwiftUI - Half modal?

iOS 16+

It looks like half sheet is finally supported in iOS 16.

To manage the size of sheet we can use PresentationDetent and specifically presentationDetents(_:selection:)

Here's an example from the documentation:

struct ContentView: View {
    @State private var showSettings = false
    @State private var settingsDetent = PresentationDetent.medium

    var body: some View {
        Button("View Settings") {
            showSettings = true
        }
        .sheet(isPresented: $showSettings) {
            SettingsView()
                .presentationDetents:(
                    [.medium, .large],
                    selection: $settingsDetent
                 )
        }
    }
}

Note that if you provide more that one detent, people can drag the sheet to resize it.

Here are possible values for PresentationDetent:

  • large
  • medium
  • fraction(CGFloat)
  • height(CGFloat)
  • custom<D>(D.Type)

SwiftUI Custom Half Modal Calculator Not Working

The problem is in your func halfSheet() and struct HalfSheetHelper. You have created a UIViewControllerRepresentable view, but it does not handle updates.

Once the sheet has already been shown, the sequence of events happening is:

  1. Pressing a button triggers a change to self.value inside PGQuestion1.
  2. SwiftUI re-renders PGQuestion1, and a new closure is passed to .halfSheet { ... } which uses the new value.
  3. Since the HalfSheetHelper is UIViewRepresentable, SwiftUI calls your updateUIViewController() function. A completely new CustomHostingController is created. Then nothing else happens because showSheet is false.

To handle updates properly, I recommend you create a Coordinator class inside your HalfSheetHelper. The coordinator is a class that SwiftUI will keep alive as long as the view is being used, and it can maintain a persistent reference to the CustomHostingController. Then in updateUIViewController(), you can use the coordinator to access the hosting controller and re-assign its rootView with the newly updated sheet contents. For more on these techniques, see the Interfacing with UIKit tutorial.

I also changed how showSheet is handled so that it becomes false only once the sheet is dismissed. This required adding a custom onDismiss closure to the CustomHostingController which it calls in viewDidDisappear.

(There still seems to be a bug with the half-sheet, where if I swipe down to dismiss the sheet and then show it again, it appears fullscreen instead of half-screen. I'm not familiar enough with the presentationController/detents APIs to figure out why this is happening!)

struct HalfSheetHelper<SheetView: View>: UIViewControllerRepresentable {
  var sheetView: SheetView
  @Binding var showSheet: Bool

  class Coordinator {
    let dummyController = UIViewController()
    let sheetController: CustomHostingController<SheetView>
    init(sheetView: SheetView, showSheet: Binding<Bool>) {
      sheetController = CustomHostingController(rootView: sheetView, onDismiss: { showSheet.wrappedValue = false })
      dummyController.view.backgroundColor = .clear
    }
  }
  func makeCoordinator() -> Coordinator {
    return Coordinator(sheetView: sheetView, showSheet: $showSheet)
  }
  func makeUIViewController(context: Context) -> UIViewController {
    return context.coordinator.dummyController
  }
  func updateUIViewController(_ uiViewController: UIViewController, context: Context) {
    context.coordinator.sheetController.rootView = sheetView

    if showSheet && uiViewController.presentedViewController == nil {
      uiViewController.present(context.coordinator.sheetController, animated: true)
    }
  }
}

class CustomHostingController<Content: View>: UIHostingController<Content> {
  var onDismiss: (() -> Void)?
  convenience init(rootView: Content, onDismiss: @escaping () -> Void) {
    self.init(rootView: rootView)
    self.onDismiss = onDismiss
  }

  override func viewDidLoad() {
    if let presentationController = presentationController as? UISheetPresentationController {
      presentationController.detents = [
        .medium(),
        .large()
      ]
      presentationController.prefersGrabberVisible = true
    }
  }

  override func viewDidDisappear(_ animated: Bool) {
    onDismiss?()
  }
}

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