I just gave a example.You should read what is binding loop.It clearly says you have a binding loop.
settings.extendExportFile is bound to textfieldId.text
textfieldId.text is bound to settings.extendExportFile
Whenever settings.extendExportFile changes which trigger a signal to change textfieldId.text and in turn this trigger a signal to change settings.extendExportFile.This will be happening in a loop, which is known as binding loop.
@CharlieG AFAIK inputMethodHints is related to the virtual keyboard. Depending upon the flags the correspoding keyboard will be invoked(like for eg. numerical keypad only or the both). Use validator instead. In your case for eg: