Flutter TextField inputFormatters not wokring with my custom regex-CodePudding

I want to allow this kind of input to my text field:

123
*123#
*123*4#

so I created and tested RegExr website this regex:

\**\d \**\d \#?

but when i try to type nothing is typed in the text field

code of using:

     ...

     keyboardType = TextInputType.phone;

     // to allow digits with asterik and hash
     final regex = RegExp(r'\**\d \**\d \#?');

     inputFormatters = [FilteringTextInputFormatter.allow(regex)];

     return TextField(
      ...
      keyboardType: keyboardType,
      inputFormatters: inputFormatters,
     );

CodePudding user response：

You can use

^\*?(?:\d \*?(?:\d #?)?)?$

See the regex demo.

Details:

^ - start of string
\*? - an optional * char
(?:\d \*?(?:\d #?)?)? - an optional sequence of
- \d - one or more digits
- \*? - an optional *
(?:\d #?)? - an optional sequence of one or more digits and an optional # char
$ - end of string.

CodePudding user response：

If you also want to match a variation with a single digit like *1# you might use a negative lookahead excluding what can not be present:

^(?!.*\*[*#]|\d*#$)[*\d]*#?$

Explanation

^ Start of string
(?! Negative lookahead, assert what to the right is not
- .*\*[*#] Match either ** or *#
- | Or
- \d*#$ Match optional digits and # at the end of the string
) Close lookahead
[*\d]*#? Match optional * chars or digits and optional #
$ End of string

See a regex demo.