HomeViewController.swift

override func viewDidLoad() {
  
  // assign bar button, to left bar item
  let profileLeft = UIBarButtonItem(image: #imageLiteral(resourceName: "user-icon"), style: .plain, target: nil, action: #selector(HomeViewController.toProfile(_:)))
  self.navigationItem.leftBarButtonItem = profileLeft
}

func toProfile(_ sender: UIButton) {
  // set root to UserProfileViewController
  let controller = UserProfileViewController()
  let userProfileViewController = UINavigationController(rootViewController: controller)
  self.window.rootViewController = userProfileViewController
}