iUI8 v1.20 includes a new view named FloatLabeledEditText. It is a modified TextField that instead of hiding the hint text when the text field is non-empty it moves it to the top.
It is implemented as a custom view. You just need to a reference to iUI8 library and then add the view with the designer (it will appear under CustomView menu).
It is based on this open source project: https://github.com/jverdi/JVFloatLabeledTextField
Note that you need to add #MinVersion: 8 when using iUI8 library.