How to use @EnvironmentObject to share data between AppDelegate and SceneDelegate/Views in SwiftUI

Question

In SwiftUI 5.1, I want to use AppDelegate to create an userData object. userData will also contain BLE advertisement data, which will be updated from AppDelegate, too. These data should be available to the UI to display those values.

In AppDelegate I use

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    private var centralManager : CBCentralManager!
    var userData: UserData!

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

        return true
    }

In SceneDelegate I want to pass to the view using

class SceneDelegate: UIResponder, UIWindowSceneDelegate {
    @EnvironmentObject var userData: UserData

    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).

        // Use a UIHostingController as window root view controller
        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            window.rootViewController = UIHostingController(rootView:
                BeaconList().environmentObject(userData)
            )

            self.window = window
            window.makeKeyAndVisible()
        }
    }

Compiling works fine, but when running the code I get

Thread 1: Fatal error: Reading EnvironmentObject outside View.body

If I remove the

.environmentObject(userData)

I get

Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)

Essentially, I'm trying to make create and update the userData object from AppDelegate, and to display from SceneDelegate and view below.

How can I implement this?

Answer 1

Maybe you can use the UIApplication.shared.delegate to get the AppDelegate an access the user data:

class AppDelegate: UIResponder, UIApplicationDelegate {

    var userData: UserData!

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

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).

        let userData = (UIApplication.shared.delegate as! AppDelegate).userData

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