There is no known action to determine the current UIKeyboardType of the keyboard. Sure you can read the keyboard type of the UITextField but it always returns the last set keyboard type but does not reflect a user changing the keyboard type manually. The demo shows one solution I found. Read through the blog post if you want to see how that was solved.
tech.ustwo.com/2014/05/29/ios-uikeyboardtype-issue/
Out of that problem a library emerged.
https://github.com/ustwo/US2KeyboardType