SwiftUI - 來自協調器的 ObservableObject 更新

Question

UIViewControllerRepresentable 從 ViewController 接收圖像。 此圖像應可用於 SwiftUI 視圖。

可觀察對象：

class CurrentImage: ObservableObject  {
 var didChange = PassthroughSubject<Void, Never>()
 @Published var photoTaken: UIImage? = nil {didSet{didChange.send()}}
}

UIViewControllerRepresentable：

struct CameraPreviewView: UIViewControllerRepresentable  {

 var currentImage: CurrentImage

 func makeCoordinator() -> Coordinator {
  Coordinator(self)
 }

 class Coordinator: NSObject {
  let parent: CameraPreviewView

  init(_ cameraPreviewController: CameraPreviewView) {
   self.parent = cameraPreviewController
   super.init()

   // Notification receives a copy of the image taken from the ViewController:         
   NotificationCenter.default.addObserver(forName: NSNotification.Name(rawValue: "imageDidChange"), object: nil, queue: OperationQueue.main){(notification) in
    if let image = notification.userInfo?["image"] as? UIImage {

      // *****ERROR: self.parent.videoStatus.photoTaken is not accessible
      self.parent.currentImage.photoTaken = image
    }
   }
  }
 }


    func makeUIViewController(context: UIViewControllerRepresentableContext<CameraPreviewView>) -> CameraViewController {
        let cameraViewController = CameraViewController()
        return cameraViewController
    }

    // View is not updating so we don't need this
    func updateUIViewController(_ cameraViewController: CameraViewController, context: UIViewControllerRepresentableContext<CameraPreviewView>) {
    }
}

ObservableObject 是“不可訪問的”，因此我無法從協調器設置其中的圖像。 我在這里忽略了一些簡單的事情嗎？

更新 2：將值傳遞給 ObservableObject 仍然不起作用

我一直在努力解決這個問題，並嘗試了十幾種方法組合。 但是為了簡化問題，我們有一個 Coordinator，它帶有一個表示 ObservableObject 的 var。 在這種情況下，我將保持簡單並嘗試設置字符串的值。

協調員：

struct CameraPreviewView: UIViewControllerRepresentable  {

 var cameraPhoto = CurrentPhoto()

 func makeCoordinator() -> Coordinator {
  Coordinator(self)
 }

 class Coordinator: NSObject {
  let parent: CameraPreviewView
  init(_ cameraPreviewController: CameraPreviewView) {
   self.parent = cameraPreviewController
   super.init()

   NotificationCenter.default.addObserver(forName: NSNotification.Name(rawValue: "imageDidChange"), object: nil, queue: OperationQueue.main){(notification) in
    print("notice received")
    self.parent.cameraPhoto.testString = "This changed"
   }
  }
 }
}...

可觀察對象：

 class CurrentPhoto: ObservableObject  {
  @Published var testString = "Testing string"
 }

為了測試這一點，我還嘗試了以下內容：

class CurrentPhoto: ObservableObject  {

 let objectWillChange = ObservableObjectPublisher()

 var testString = "Testing String" {
  willSet {
   print("set string")
   objectWillChange.send()
  }
 }
}

在第二個示例中，會調用 willSet 方法。 （它打印“設置字符串”）但是值仍然是“測試字符串”。

ObservableObject 正在從控制器調用，但值沒有設置或更改。

因此視圖不會收到新值：

struct ContentView: View {
 @ObservedObject var cameraState = CurrentPhoto()
 var body: some View {
  VStack{
   Text("test this \(cameraState.testString)")
   ...   

注意：將值從 VIEW 傳遞給 ObservableObject 是可行的，因此問題以某種方式與協調器如何將值傳遞給 ObservedObject 相關。

以下工作並將值從視圖傳遞到 OO：

Button(action : {
 self.cameraState.testString = "from view"
}, label : {
 Text("Change string")
}

Answer 1

這並不能完全解決如何將 Coordinator 綁定到 ObservableObject 的問題。 但是，這確實實現了預期目標，即將圖像從 Coordinator 返回到 SwiftUI。

風景：

struct ContentView: View {

 @State private var photoInView: Image?
 @State var isRecording = true

 var body: some View {
  VStack{
   photoInView?
   .resizable()
   .scaledToFit() 
   ZStack (alignment: .bottom) {
   // Start up the CameraPreview and this will 2-way bind.  
   CameraPreviewView(isRecording: $isRecording, photoReceivedFromCoordinator: $photoInView)
   ....

然后在 UIViewRepresentable 中：

struct CameraPreviewView: UIViewControllerRepresentable  {

  @Binding var isRecording: Bool
  @Binding var photoReceivedFromCoordinator: Image?

  func makeCoordinator() -> Coordinator {
   Coordinator(self)
  }

  class Coordinator: NSObject {
   // Setting the coordinator to parent allows the coordinator to use the    @Binding
   let parent: CameraPreviewView
   init(_ cameraPreviewController: CameraPreviewView) {
    self.parent = cameraPreviewController
    super.init()

    NotificationCenter.default.addObserver(forName: NSNotification.Name(rawValue: "imageDidChange"), object: nil, queue: OperationQueue.main){(notification) in
    if let uiImage = notification.userInfo?["image"] as? UIImage {
     // We need an Image not a UI Image, so first we convert it
     let image = Image(uiImage: uiImage)
     // Assign the value to the parent's binding value
     self.parent.photoReceivedFromCoordinator = image
    }
   }
  }
 }