performSegue before the View is visible - ios

Question

I have two views
ViewController-> Main view
LoginVC -> LogIn View
My initial view is ViewController which contains buttons and some text.
What i want to achive
Perform a segue that will transfer the view to Login if the user is not yet log in.
What i have done
Inside my ViewController I did a check if USER_ID is nil then if its a nil then i will perform a segue.
override func viewWillAppear(animated: Bool) {
if Globals.USER_ID == nil{
self.performSegueWithIdentifier("goto_login", sender: nil)
// dispatch_async(dispatch_get_main_queue(), {
// self.performSegueWithIdentifier("goto_login", sender: nil)
// })
}
}
What is my problem
My Problem is whether I use viewWillAppear or viewDidLoad or viewDidAppear to transfer view from ViewController to LoginVC.ViewController will be visible in a single second before the the login screen appears and i want to get rid of it.Can someone help me solve this issue.

Answer 1

I have same functionality in my App. I achieved it by checking for userID in AppDelegate.swift inside function func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool
So, delete the segue and your modified code will look like as follows:
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
// Override point for customization after application launch.
let storyBoard: UIStoryboard = UIStoryboard(name: "Main", bundle: NSBundle.mainBundle())
if Globals.USER_ID == nil{
let loginScreen = storyBoard.instantiateViewControllerWithIdentifier("LoginVC")
self.window?.rootViewController = loginScreen
}else{
let mainScreen = storyBoard.instantiateViewControllerWithIdentifier("ViewController")
self.window?.rootViewController = mainScreen
}
return true
}
This way you will not need any of the method like viewDidLoad(), viewDidAppear() or viewWillAppear()to be used for this purpose.
Just as an addition to this answer - Use the instance of AppDelegate again after logout happens. For example you should do following in logout method:
func logout() {
if let appDelegate = UIApplication.sharedApplication().delegate as? AppDelegate {
Globals.USER_ID = nil
appDelegate.window?.rootViewController = loginScreen
}
}
This way you can clear the userID and navigate back to login screen after the user logouts.