為什么不更改 @ObservedObject 更新 UIViewRepresentable？

Question

我有一個簡單的例子，我在父視圖中創建一個@ObservedObject並將其傳遞給子UIViewRepresentable 。 當我單擊“按鈕”時，它會修改@ObservableObject但子視圖永遠不會更新（即永遠不會調用updateUIView ）。 有不同的方法可以做到這一點嗎？

import SwiftUI

class UpdateViewState: ObservableObject {
  @Published var words = ["A", "B", "C"]

  func addWord(word: String) {
    print("added word")
    words.append(word)
  }
}

struct UpdateView: View {
  @ObservedObject private var state = UpdateViewState()

  var body: some View {
    VStack {
      UpdateViewRepresentable(state: state)
      Text("Button").onTapGesture {
        self.state.addWord(word: "A")
      }
    }
  }
}

struct UpdateViewRepresentable: UIViewRepresentable {
  @ObservedObject var state: UpdateViewState

  func makeUIView(context: Context) -> UILabel {
    let view = UILabel()
    view.text = "Hello World"
    return view
  }

  func updateUIView(_ uiView: UILabel, context: UIViewRepresentableContext<UpdateViewRepresentable>) {
    print("updateUIView")
    uiView.text = state.words.joined(separator: ", ")
  }
}

Answer 1

嘗試這個：

public final class UpdateViewState: ObservableObject {

  @Published var words = ["A", "B", "C"]

  func addWord(word: String) {
    print("added word ", words)
    words.append(word)
  }
}

struct ContentView: View {

 @EnvironmentObject private var state: UpdateViewState

  var body: some View {
    VStack {
        UpdateViewRepresentable(state: .constant(state))
      Text("Button").onTapGesture {
        self.state.addWord(word: "A")
      }
    }.onAppear() {
        self.state.words.append("aha")
    }
  }
}

struct UpdateViewRepresentable: UIViewRepresentable {

    @Binding var state: UpdateViewState

  func makeUIView(context: Context) -> UILabel {
    let view = UILabel()
    view.text = "Hello World"
    return view
  }

  func updateUIView(_ uiView: UILabel, context: UIViewRepresentableContext<UpdateViewRepresentable>) {
    print("updateUIView")
    uiView.text = state.words.joined(separator: ", ")
  }
}

Answer 2

這可能會以一種非常簡單的方式幫助您：

var body: some View {
        VStack {
          UpdateViewRepresentable(state: state)
          Text("Button").onTapGesture {
            self.state.addWord(word: "A")
            self.state.objectWillChange.send()
          }
        }
    }

嘗試使用我添加的行，這將使視圖自行更新。 確保您使用：

import Combine