class UIExtension: UIViewController {

    func prepareAlert(title: String, message: String) -> UIAlertController {
        let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)
        alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: nil))
        return alert
    }

}

class FirstViewController: UIExtension {

    //somewhere inside used the following
    present(prepareAlert(title: "Error Validation", message: "invalid fields"), animated: true, completion: nil)

}