ios - performSegue before the View is visible -

i have 2 views

viewcontroller-> main view loginvc -> login view 

my initial view viewcontroller contains buttons , text.

what want achive

perform segue transfer view login if user not yet log in.

what have done

inside viewcontroller did check if user_id nil if nil perform 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 problem

my problem whether use viewwillappear or viewdidload or viewdidappear transfer view viewcontroller loginvc.viewcontroller visible in single second before the login screen appears , want rid of it.can me solve issue.

i have same functionality in app. achieved checking userid in appdelegate.swift inside function func application(application: uiapplication, didfinishlaunchingwithoptions launchoptions: [nsobject: anyobject]?) -> bool

so, delete segue , modified code follows:

  func application(application: uiapplication, didfinishlaunchingwithoptions launchoptions: [nsobject: anyobject]?) -> bool {     // override point 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 not need of method viewdidload(), viewdidappear() or viewwillappear()to used purpose.

just addition answer - use instance of appdelegate again after logout happens. example should following in logout method:

func logout() {         if let appdelegate = uiapplication.sharedapplication().delegate as? appdelegate {             globals.user_id = nil             appdelegate.window?.rootviewcontroller = loginscreen         } } 

this way can clear userid , navigate login screen after user logouts.