对 ObservedObject 的更改不会更新 UIViewRepresentable

Question

下面是最简单的例子。在预览中工作正常（UITextView文本更新为“哎哟”）。但是，在一个应用程序中运行它（即添加为rootView通过sceneDelegate），以及UITextView不更新。

import SwiftUI

class ModelObject : ObservableObject{
    @Published var text = "Model Text"
}

struct MyTextView : UIViewRepresentable {
    @ObservedObject var modelObject : ModelObject

    func makeUIView(context: Context) -> UITextView {
        let result = UITextView()
        result.isEditable = true
        return result
    }
    func updateUIView(_ view: UITextView, context: Context) {
        view.text = modelObject.text
    }
}

struct BugDemoView : View{
    @ObservedObject var modelObject : ModelObject
    var body : some View{
        VStack{
            MyTextView(modelObject: modelObject)
            Button(action: {
                self.modelObject.text = "ouch"
            }){
                Text("Button")
            }
        }
    }
}

#if DEBUG

var mo = ModelObject()

struct BugDemoView_Preview: PreviewProvider {
    static var previews: some View {
        BugDemoView(modelObject: mo)
    }
    
}
#endif

Answer 1

它看起来像是 SwiftUI 的某种错误，但有两种解决方法：

1. 将字符串传递 @Binding给MyTextView：

struct MyTextView : UIViewRepresentable {
    @Binding var text: String

    func makeUIView(context: Context) -> UITextView {
        let result = UITextView()
        result.isEditable = true
        return result
    }
    func updateUIView(_ view: UITextView, context: Context) {
        view.text = text
    }
}

struct BugDemoView : View{
    @ObservedObject var modelObject = ModelObject()
    var body : some View{
        VStack{
            MyTextView(text: $modelObject.text)
            Button(action: {
                self.modelObject.text = "ouch"
            }){
                Text("Button")
            }
        }
    }
}

2. 将字符串传递给MyTextView：

struct MyTextView : UIViewRepresentable {
    var text: String

    func makeUIView(context: Context) -> UITextView {
        let result = UITextView()
        result.isEditable = true
        return result
    }
    func updateUIView(_ view: UITextView, context: Context) {
        view.text = text
    }
}

struct BugDemoView: View{
    @ObservedObject var modelObject = ModelObject()
    var body: some View{
        VStack{
            MyTextView(text: modelObject.text)
            Button(action: {
                self.modelObject.text = "ouch"
            }){
                Text("Button")
            }
        }
    }
}