如何创建一个发射键盘高度的RxSwift观察体？

var keyboardHeightObservable: Observable<CGFloat>?

keyboardHeightObservable = Observable
    .from([
        NotificationCenter.default.rx.notification(UIResponder.keyboardWillShowNotification)
            .map { notification -> CGFloat in
                (notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue.height ?? 0
            },
        NotificationCenter.default.rx.notification(UIResponder.keyboardWillHideNotification)
            .map { _ -> CGFloat in
                0
            }
    ])
    .merge()

keyboardHeightObservable?
    .subscribe(onNext: { keyboardHeight in
        // 处理键盘高度变化的逻辑
        print("键盘高度：\(keyboardHeight)")
    })
    .disposed(by: disposeBag)