Why don't changes to @ObservedObject update a UIViewRepresentable?

Question

I have this simple example where I'm creating an @ObservedObject in a parent view and passing it to a child UIViewRepresentable . When I click "Button", it modifies the @ObservableObject but the child view never gets updated (ie updateUIView is never called). Is there a different way to do this?

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

try this:

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

This may help you in a very simple way:

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

Try to use the line I added, this will the View to update itself. Make sure you use:

import Combine