struct ContentView: View {
   @State private var appData = ApplicationData.shared

   var body: some View {
      VStack {
         Text(appData.showValue)
         Button("Add Value") {
            appData.myObject.testValue += 100
         }.buttonStyle(.borderedProminent)
         Spacer()
      }.padding()
      .onDisappear {
         appData.myObserver = nil
      }
   }
}