how can i use RegExp to detecting duplicated specific input in string variables-CodePudding

dart flutter

i need regular expression to know if a string variable than coming from user inputs contains more than 1 same input

wanted inputs that i want handle it (- _ .)

the wanted input that i won't be repeated more than once is - or . or _

lets say user wrote Alex.9 .. well it is sound good because he wrote one dot well i already know how to handle in case there are two dot next to each other like Alex..9 with using contains('..'), but if those two dots were not next to each other like A.le.x result will be false

what i want by no and ok :=

Alex.9 => ok
A.le.x => no
Alex-9 => ok
A-le-x9 => no
Alex_9 => ok
Al_e_x9 => no


 // also if there was two or the whole difference  of (- _ .) in the same string. like
 A.le-x => no
 A.le_x => no
 A-l_9 => no
 A.l-x_9 => no

sample of what i mean

final TextEditingController nameController = TextEditingController();
Scaffold(
body: nameController.text.contains(RegExp('Is - or _ or . duplicated?'))?
      Text('yes duplicated') : Text('not duplicated'),
);

CodePudding user response：

regular expression: [._-](.*[._-])