Question

I try to enable/disable Command Menu buttons of the App based on the DetailView appeared or not (view appeared = button enabled). For that I try to use @EnvironmentalObject to receive the current condition via an ViewState class using it to enable/disable the button:

@main
 struct MyApp: App {
  ...
  
  // access viewState via Environmental Object
  @EnvironmentObject var viewState: ViewState

  var body: some Scene {
    WindowGroup {
    ...
    }

    .commands {
        
      // changing "File" menu list
      CommandGroup(after: CommandGroupPlacement.undoRedo) {
        
        Button("Listeneintrag bearbeiten") {
            // do stuff
        }.disabled(!viewState.itemSelected)  // <-- ERROR OCCURING
      }
    }
 }
}

具有变量的观测目标

class ViewState : ObservableObject {

  @Published var userSelected = false
  @Published var itemSelected = false
}

详细情况观点的出现应确定国家:

struct DetailsView: View {
 ...
 @StateObject var viewState = ViewState()

 var body: some View {
    ZStack(alignment: .bottom) {
  ...
 }
 .onAppear {
    viewState.userSelected = true
 }
 .onDisappear {
    viewState.userSelected = false
 }
}

错误信息是:<条码> 发现的类型观点的目的。 A View.environmentObject (_:) for ViewState may beshed as an ancestor of this view.

My approach might be completely wrong but I used it to share information from App to the views successfully. I did not find any information on how to pass data/information from views to the (main) app struct. Any hint?

Answer 1

Your error is telling you that in your App, there is no viewState model. This is because you have to declare your viewState (the single source of truth) in the parent of your view hierarchy, to be passed down to other views. And App is the top most in the view hierarchy.

因此,在你宣布<代码>@时尝试采用这种做法。国家申请中反对国=观点国(),并将这一模式传达给您的其他意见。这使你在申请与其他意见之间有两种方式的<条码>通信,,反之亦称<>。

例:

import SwiftUI @main struct MyApp: App { @StateObject var viewState = ViewState() // <--- here var body: some Scene { WindowGroup { ContentView() .environmentObject(viewState) // <--- here } .commands { CommandGroup(after: CommandGroupPlacement.undoRedo) { Button("Listeneintrag bearbeiten") { // ... }.disabled(!viewState.itemSelected) } } } } class ViewState : ObservableObject { @Published var userSelected = false @Published var itemSelected = false } struct ContentView: View { var body: some View { // ... DetailsView() } } struct DetailsView: View { @EnvironmentObject var viewState: ViewState // <--- here var body: some View { VStack { Text("DetailsView") Button("Enable/Disable Listeneintrag bearbeiten button") { // <-- for testing viewState.itemSelected.toggle() } } .onAppear { viewState.userSelected = true } .onDisappear { viewState.userSelected = false } } }

查阅官方链接后,它向您提供了一些良好实例,说明如何在你的附录中管理数据:。请注意,如果你是爱心17,见。 a. 管理你的模型数据。

友情链接