iOS mobile application first ever app launch detect

Question

I was trying to initiate an integer value in UserDefaults. But I want to do this operation once. At the first launch.

func application(_: UIApplication, didFinishLaunchingWithOptions _: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.
        UserDefaults.standard.set(-1, forKey: Constant.shared.empId)
       return true
    }

I tried this the above way. But didFinishLaunchingWithOptions is calling every time I launch the app. is there any function that is called once during the app's whole life cycle?

Answer 1

First, you can check whether userDefault contains any value or not. If it doesn't have any value, then you can set it. Following code may help you.

if UserDefaults.standard.object(forKey: Constant.shared.empId) != nil {
            
    print("UserDefaults has a value")
}
else {
    print("UserDefaults doesn't have a value")
    UserDefaults.standard.set(-1, forKey: Constant.shared.empId)
}

Answer 2

You need call:

UserDefaults.standard.register(
  defaults: {
    Constant.shared.empId: -1
  }
)

It will be called every time on app launch, but will not override value set with set method.