Hi there, as the title states, I get the following warning from my custom field type code:
Notice: Undefined variable: parent in ...acf/string-pair-acf4.php on line 41
The line causing it is this (taken from your GitHub example):
// do not delete!
EDIT: I am still using an old approach, including the file directly from my theme.
Sorry, question solved. I just had to remove the $parent variable, of course *facepalm*