enum AlertActionType: String {
    case One
    case Two
    case Three
}

let firstAction = RxAlertAction(title: "first", style: .default, identifier: AlertActionType.One)
let secondAction = RxAlertAction(title: "second", style: .cancel, identifier: AlertActionType.Two)
let thirdAction = RxAlertAction(title: "third", style: .destructive, identifier: AlertActionType.Three)
let alert = UIAlertController(title: "Hello world!", message: nil, preferredStyle: .alert)

alert.addAction(firstAction)
alert.addAction(secondAction)
alert.addAction(thirdAction)

present(alert, animated: true)

Observable.merge(firstAction.asObservable(), secondAction.asObservable(), thirdAction.asObservable())
    .take(1)
    .subscribe(onNext: { print("Selected: \($0)") })
    .disposed(by: bag)