Partial matching a string against a regex in swift

Question

I'm trying to create regexp with format "dd-dd-dd" in Swift

I came up with this :

(\d{1,2})(-)(\d{1,2})(-)(\d{1,2})

This pattern gives me correct result if the string is given as a whole. Example :

12-32-42 -> correct
2-32-1   -> correct
2--32-3  -> incorrect

I will be using this pattern in textfields. What I would like to know is if the typed string is heading towards positive regexp check. Example :

12     -> correct
-12-32 -> correct
12-    -> correct
-12--  -> incorrect

I will be grateful for any help you can provide.

Why is -12-32 correct? It starts with -. I'd suggest let pattern = "^\\d{1,2}(?:-(?:\\d{1,2}(?:-\\d{0,2})?)?)?$", see regex101.com/r/eHHG2l/1. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Apr 16, 2019 at 18:45

The fourth bird · Accepted Answer · 2019-04-16 17:22:34Z

1

One option could be to list to possible combinations in an alternation:

^(?:\d{1,2}-\d{1,2}-\d{1,2}|\d{1,2}-|-\d{1,2}-\d{1,2}|\d{1,2})$

answered Apr 16, 2019 at 16:55

The fourth bird

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1 Comment

Maybe not perfect, but it works and that's exactly what l wanted. Thank you!