/// An observable keyboard frame.
let frame: Driver<CGRect>

/// An observable visible height of keyboard. Emits keyboard height if the keyboard is visible
/// or `0` if the keyboard is not visible.
let visibleHeight: Driver<CGFloat>

/// Same with `visibleHeight` but only emits values when keyboard is about to show. This is
/// useful when adjusting scroll view content offset.
let willShowVisibleHeight: Driver<CGFloat>

RxKeyboard.instance

RxKeyboard.instance.frame
  .drive(onNext: { frame in
    print(frame)
  })
  .disposed(by: disposeBag)