RegExp for numbers 024648-4568 in dart

Question

I am using Flutter and dart and I want RegExp to validate strings in the 024648-4568 like format, where a user can only put six numbers at the start, then a - and then 4 digits at the end.

I started with RegExp(r'^\d{1,6}[\-]?\d{4}'), but could not fix it for the subsequent dash and 4 digits.

In Flutter, I use it like this:

inputFormatters: [new FilteringTextInputFormatter.allow( RegExp(r'^\d{1,6}-\d{4}') ,]

Why? What was the problem? Adding `-`? Then `\d{4}`? And the string end anchor? `$`? — Wiktor Stribiżew, Jun 11 '21 at 09:29
Do you mean like this: RegExp(r'^\d{1,6}[\-]?\d{4}') this dose not worked for me in Flutter. — blue492, Jun 11 '21 at 09:56
You must add the whole relevant code to your question. And no, I clearly meant `RegExp(r'^\d{1,6}-\d{4}$')` — Wiktor Stribiżew, Jun 11 '21 at 10:03
Did you tested that in Flutter like this: because it did worked for me, inputFormatters: [new FilteringTextInputFormatter.allow( RegExp(r'^\d{1,6}-\d{4}') ,], with your solution I can not write any input — blue492, Jun 11 '21 at 11:08
*A TextInputFormatter that prevents the insertion of characters matching (or not matching) a particular pattern.* - the validation triggers for each input char, right? That is why it can't work in general. Try a regex that matches all of these as optional chars except the first digit, `RegExp(r'^\d{1,6}(?:-\d{0,4})?$')` — Wiktor Stribiżew, Jun 11 '21 at 11:13

score 3 · Answer 1 · answered Jun 11 '21 at 14:52

You need to make sure the regular expression you use in the FilteringTextInputFormatter can match a zero- or one-char length string. For example, you can use

RegExp(r'^\d{1,6}(?:-\d{0,4})?$')

See the regex demo. The {1,6} limiting quantifier makes the first digit required in the input.

More details:

^ - start of string
\d{1,6} - one to six digits
(?:-\d{0,4})? - an optional sequence of
- - - a hyphen
- \d{0,4} - zero to four digits
$ - end of string.

RegExp for numbers 024648-4568 in dart

1 Answers1