为什么不更改 @ObservedObject 更新 UIViewRepresentable？

Question

我有一个简单的例子，我在父视图中创建一个@ObservedObject并将其传递给子UIViewRepresentable 。 当我单击“按钮”时，它会修改@ObservableObject但子视图永远不会更新（即永远不会调用updateUIView ）。 有不同的方法可以做到这一点吗？

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

尝试这个：

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

这可能会以一种非常简单的方式帮助您：

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

尝试使用我添加的行，这将使视图自行更新。 确保您使用：

import Combine