tab bar key board issue swift 3

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "showLogin"{

        let bottomBar = segue.destinationViewController as LoginViewController
println("showLogin seque called")

        bottomBar.navigationItem.hidesBackButton = true // hide back button
bottomBar.hidesBottomBarWhenPushed = true // hide bar menu
    }

}