middleName constant
The input field expects a person's middle name.
This hint will be translated to the below values on different platforms:
- Android: AUTOFILL_HINT_PERSON_NAME_MIDDLE.
 - iOS: middleName.
 - web: "additional-name".
 - Otherwise, the hint string will be used as-is.
 
Implementation
static const String middleName = 'middleName';