Presenting from detached view controllers in Swift

detached-vc-solution.swift

// UIViewController extension to get root VC
func getRootViewController(of nestedViewController: UIViewController) -> UIViewController? {
  return nestedViewController.view.window?.rootViewController
}

// In use inside non-root VC
let vc = UINavigationController(rootViewController: CurrencySelectorViewController(type: type))
vc.modalPresentationStyle = .overFullScreen

if let root = getRootViewController(of: self) {
  root.present(vc, animated: true, completion: nil)
}