SwiftUI: Changing variables in ContentView from functions inside AppDelegate

Question

So I have a register for push notifications function in AppDelegate.

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
var toggler: Toggler?


func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    // Override point for customization after application launch.
    return true
}

// MARK: UISceneSession Lifecycle

func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {
    // Called when a new scene session is being created.
    // Use this method to select a configuration to create the new scene with.
    return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)
}

func application(_ application: UIApplication, didDiscardSceneSessions sceneSessions: Set<UISceneSession>) {
    // Called when the user discards a scene session.
    // If any sessions were discarded while the application was not running, this will be called shortly after application:didFinishLaunchingWithOptions.
    // Use this method to release any resources that were specific to the discarded scenes, as they will not return.
}  
}

In ContentView, I have a toggle that I want to use to turn the authorization on and off. With that being said, the toggle in ContentView is an @State variable that I thought should have its value set by the registerForPushNotifications() function.

struct ContentView: View {
@EnvironmentObject var toggler: Toggler

var body: some View {
    
    VStack {
        Toggle(isOn: toggler.$toggleOn) {
            Text("Toggle Label")
        }
    }
    
}

}

Scene Delegate is as follows:

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

var window: UIWindow?


func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
    // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
    // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
    // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).

    // Create the SwiftUI view that provides the window contents.
    
    let toggler = Toggler()
    if let appDelegate = UIApplication.shared.delegate as? AppDelegate {
        appDelegate.toggler = toggler
    }
    let contentView = ContentView().environmentObject(toggler)

    // Use a UIHostingController as window root view controller.
    if let windowScene = scene as? UIWindowScene {
        let window = UIWindow(windowScene: windowScene)
        window.rootViewController = UIHostingController(rootView: contentView)
        self.window = window
        window.makeKeyAndVisible()
    }
}

func sceneDidDisconnect(_ scene: UIScene) {
    // Called as the scene is being released by the system.
    // This occurs shortly after the scene enters the background, or when its session is discarded.
    // Release any resources associated with this scene that can be re-created the next time the scene connects.
    // The scene may re-connect later, as its session was not neccessarily discarded (see `application:didDiscardSceneSessions` instead).
}

func sceneDidBecomeActive(_ scene: UIScene) {
    // Called when the scene has moved from an inactive state to an active state.
    // Use this method to restart any tasks that were paused (or not yet started) when the scene was inactive.
}

func sceneWillResignActive(_ scene: UIScene) {
    // Called when the scene will move from an active state to an inactive state.
    // This may occur due to temporary interruptions (ex. an incoming phone call).
}

func sceneWillEnterForeground(_ scene: UIScene) {
    // Called as the scene transitions from the background to the foreground.
    // Use this method to undo the changes made on entering the background.
}

func sceneDidEnterBackground(_ scene: UIScene) {
    // Called as the scene transitions from the foreground to the background.
    // Use this method to save data, release shared resources, and store enough scene-specific state information
    // to restore the scene back to its current state.
}


}

And Toggle looks like:

class Toggler: NSObject, ObservableObject {
    @State var toggleOn: Bool = false
}

Here is the approach you can adapt https://stackoverflow.com/a/59380382/12299030 — Asperi, Aug 14 '20 at 14:54
@Asperi I got it to compile using the same method you used in the stack overflow post you referenced. When I try to actually toggle the switch though, I get the following error: invalid mode 'kCFRunLoopCommonModes' provided to CFRunLoopRunSpecific - break on _CFRunLoopError_RunCalledWithInvalidMode to debug. This message will only appear once per execution. This error happens once when I press the toggle (which does not visibly change) and then if I press the toggle again there are no more errors. — nickcoding, Aug 14 '20 at 15:21
@Asperi Toggle() requires a binding bool though--Published variables aren't Binding so how do I initialize the Toggle() in ContentView? Also if this works and you want some points just put down an answer so I can mark it as correct — nickcoding, Aug 14 '20 at 16:04

score 1 · Accepted Answer · answered Aug 14 '20 at 17:16

Here is code to finish, everything else you did correct

class Toggler: ObservableObject {
    @Published var toggleOn: Bool = false
}

struct ContentView: View {
  @EnvironmentObject var toggler: Toggler

  var body: some View {
    VStack {
        Toggle(isOn: self.$toggler.toggleOn) { // << binding via EnvironmentObject
            Text("Toggle Label")
        }
    }
  }
}

SwiftUI: Changing variables in ContentView from functions inside AppDelegate

1 Answers1