This example illustrates how to push a view controller to the top of the navigation stack

ViewControllerA.swift

import UIKit

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }


    @IBAction func handleLoginAction(_ sender: Any) {
        /* Step 1  */
        /*
         * This example is when we want to push a view controller to the top of the navigation backstack
         */
        let storyBoard : UIStoryboard = UIStoryboard(name: "Main", bundle:nil)
        let viewControllerB = storyBoard.instantiateViewControllerWithIdentifier("nextView") as! ViewControllerB
        self.presentViewController(viewControllerB, animated:true, completion:nil)
    }
}