Present View Controller in Storyboard with a Navigation Controller - Swift

You're definitely on the right track. Unfortunately when you reference a view controller by its storyboard ID it will ignore the fact it is embedded within anything. Same goes for segues when you segue to something embedded, the destination view controller will be the embedding controller, not the controller you're usually interested in. Anyhow, you should be able to fix the problem in a similar way you've done in Objective-C, so this is just an exercise in syntax porting.

Edit: Define storyboard name with string now

let storyboard : UIStoryboard = UIStoryboard(name: "AccountStoryboard", bundle: nil)
let vc : WelcomeViewController = storyboard.instantiateViewControllerWithIdentifier("WelcomeID") as WelcomeViewController
vc.teststring = "hello"        

let navigationController = UINavigationController(rootViewController: vc)

self.presentViewController(navigationController, animated: true, completion: nil)

OR you can give your embedding view controller an ID and instantiate that instead.

 let secondViewController = self.storyboard?.instantiateViewControllerWithIdentifier("WelcomeID") as SecondViewController

        self.navigationController?.pushViewController(secondViewController, animated: true)

Class Name is : SecondCiewController