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How to add an AppDelegate to a SwiftUI app

Paul Hudson    @twostraws   

Updated for Xcode 12.0

New in iOS 14

SwiftUI apps launch using a custom struct that conforms to the App protocol, but sometimes you might want to get back the old UIApplicationDelegate functionality we used to have – perhaps to handle registration for push notifications, to respond to memory warnings, to detect time changes, and so on.

To do this, first create a custom class that inherits from NSObject and conforms to the UIApplicationDelegate protocol, like this:

class AppDelegate: NSObject, UIApplicationDelegate {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]? = nil) -> Bool {
        print("Your code here")
        return true
    }
}

I’ve added didFinishLaunchingWithOptions in there, but you only need to implement the methods you care about.

And now in your App scene, use the UIApplicationDelegateAdaptor property wrapper to tell SwiftUI it should use your AppDelegate class for the application delegate.

@main
struct NewIn14App: App {
    @UIApplicationDelegateAdaptor(AppDelegate.self) var appDelegate

    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

SwiftUI is responsible for creating that delegate and looking after its lifetime, so you can go ahead and add any other app delegate functionality to that class to have it called.

Tip: For push notifications, you should probably adjust the delegate property of UNUserNotificationCenter.current()` so that it points to a custom class you own.

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