userPinValidator function
Implementation
String? userPinValidator(dynamic val) {
final String value = val as String;
if (value.isEmpty) {
return 'A PIN is required';
}
if (!RegExp(r'^-?[0-9]+$').hasMatch(value)) {
return 'Only digits are allowed, 0-9';
}
if (value.length < 4) {
return 'Enter a four digit PIN';
}
return null;
}