如何在SwiftUI中从类向结构体传值？

Question

我得到了一个类，其中我初始化了@Published var display，它接收函数imagePickerController中detectFlower()的结果。

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
    }

}

其中我初始化了@Published var display，它接收imagePickerController函数中的detectFlower()函数的结果。在ScanWithCamera结构中，我想用这个值在Text()中设置一个文本。我在结构@EnvironmentObject中初始化了var env: ImagePickerCoordinator，并设置了Text(env.display)，但我得到了一个Fatal错误。No ObservableObject of type ImagePickerCoordinator found. ImagePickerCoordinator的View.environmentObject(_:)作为这个视图的祖先可能会丢失。

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)
        }
    }
}

如何将这个文本从类函数传递到结构体？

Answer 1

添加你的 场景代表

let env = ImagePickerCoordinator()

并添加到你的rootViewController中。

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

现在你的ImagePickerCoordinator已经连接到你的环境了。

而且不要使用 @Binding 在您的班级中。

使用 @Published 图像 "和 "isShown "的变量，然后你可以通过 env.image 例如在您的ScanWithCamera-View中。