How to pass value from class to struct in SwiftUI

Question

I got class:

class ImagePickerCoordinator: NSObject, UINavigationControllerDelegate, UIImagePickerControllerDelegate, ObservableObject{

    @Published var display = "Name"

    @Binding var image: UIImage?
    @Binding var isShown: Bool

    init(image: Binding<UIImage?>, isShown: Binding<Bool>){
        _image = image
        _isShown = isShown
    }

    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {

        if let uiImage = info[UIImagePickerController.InfoKey.originalImage] as? UIImage {

            guard let convertedCIImage = CIImage(image: uiImage) else {
                fatalError("Cannot convert UIImage to CIIMage.")
            }

            detectFlower(image: convertedCIImage) { (flowerString, error) in

                self.display = flowerString!

            }

            image = uiImage
            isShown = false
        }
    }

    func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
        isShown = false
    }

    func detectFlower(image: CIImage,completion: @escaping (_ getString:String?,_ error:Error?)-> Void)  {
     guard let model = try? VNCoreMLModel(for: FlowerModels().model) else {

         fatalError("Cannot import a model.")
     }

     let request = VNCoreMLRequest(model: model) { (request, error) in

         let classification = request.results?.first as? VNClassificationObservation

        let nameOfFlower = String(classification?.identifier ?? "Unexpected type")

         completion(nameOfFlower,nil)

     }

     let handler = VNImageRequestHandler(ciImage: image)

     do {
         try handler.perform([request])
     } catch {
         print(error)
           completion(nil,error)
     }
    }
}

struct ImagePicker: UIViewControllerRepresentable {

    typealias UIViewControllerType = UIImagePickerController
    typealias Coordinator = ImagePickerCoordinator

    @Binding var image: UIImage?
    @Binding var isShown: Bool
    var sourceType: UIImagePickerController.SourceType = .camera

    func updateUIViewController(_ uiViewController: UIImagePickerController, context: UIViewControllerRepresentableContext<ImagePicker>) {
    }

    func makeCoordinator() ->ImagePicker.Coordinator {
        return ImagePickerCoordinator(image: $image, isShown: $isShown)
    }

    func makeUIViewController(context: UIViewControllerRepresentableContext<ImagePicker>) -> UIImagePickerController {

        let picker = UIImagePickerController()
        picker.sourceType = sourceType
        picker.delegate = context.coordinator

        return picker
    }

}

in which I initialized @Published var display which receives the result of the detectFlower() function that is in the function imagePickerController. In structure ScanWithCamera I'd like to use this values to set a text in Text(). I initialized in struct @EnvironmentObject var env: ImagePickerCoordinator and set Text(env.display), but I get a Fatal error: No ObservableObject of type ImagePickerCoordinator found. A View.environmentObject(_:) for ImagePickerCoordinator may be missing as an ancestor of this view.

struct ScanWithCamera: View {

    @State private var showSheet: Bool = false
    @State private var showImagePicker: Bool = false
    @State private var sourceType: UIImagePickerController.SourceType = .camera

    @State private var userImage: UIImage?
    @EnvironmentObject var env: ImagePickerCoordinator

    var body: some View {

        NavigationView{
            VStack{
                Text(env.display)
                    .foregroundColor(.blue)
                    .font(.system(size: 25))

                Image(uiImage: userImage ?? UIImage(named: "flower_logo")!)
                    .resizable()
                    .aspectRatio(contentMode: .fit)
                    .frame(width: 400, height: 400)

            }
            .frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: .infinity, alignment: .top)

        }
        .navigationBarTitle(Text(""), displayMode: .inline)
        .navigationBarItems(trailing:
                HStack {
                    Button("Camera") {
                        self.showImagePicker = true
                        self.sourceType = .photoLibrary
                        print("Camera tapped!")
                    }
                }
        )
        .sheet(isPresented: $showImagePicker) {
            ImagePicker(image: self.$userImage, isShown: self.$showImagePicker, sourceType: self.sourceType).environmentObject(self.env)
        }
    }
}

How is the way to pass this text from class function to struct?

Kuhlemann · Accepted Answer · 2020-05-19 18:21:36Z

1

Add in your SceneDelegate

let env = ImagePickerCoordinator()

And add to your rootViewController:

window.rootViewController = UIHostingController(rootView: contentView.environmentObject(env))

Now your ImagePickerCoordinator is connected to your environment.

And don't use @Binding in your Class.

Use @Published for "image" and "isShown" in your class too. You can then access all those variables by env.image for example in your ScanWithCamera-View.

edited May 19, 2020 at 18:21

answered May 19, 2020 at 18:15

Kuhlemann

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