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Asked: 2026-06-17T21:45:40+00:00

Here is a regex pattern I created in Objective C: ^\n?([#]{1,2}$|[*]{1,2}$|[0-9]{1,3}.$) I want to

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Here is a regex pattern I created in Objective C:

^\n?([#]{1,2}$|[*]{1,2}$|[0-9]{1,3}.$)

I want to match:

  1. starts with \n or empty
  2. ends with # or * or .
  3. if ends with . there will be 1 or 2 or 3 digits in between
  4. If ends with # or *, there could be 1 more # or * in between

The regex I created matches ‘\n1#’ which is not what I want.
Can anyone help me correct this? Is this fastest one? The regex will be used frequently, so I want it to be as fast as possible.

UPDATE:

Here’s a sample strings for testing:

"\n#", "11*1", "1#", "a1.", "111*", "\n1#", "\n11.", "a11.", "1. ", "*1."

The 1# and 111* were matched. Not sure what went wrong.

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1 Answer

  1. Editorial Team

    You’re matching #1 and 111# because of [0-9]{1,3}.. You haven’t escaped the . and this group basically matches any sequence of 1 to 3 digits followed by any character.

    What you’re looking for is

    ^\n?(#{1,2}|\*{1,2}|[0-9]{1,3}\.)$

    Properly escaped in ObjC, it would be

    @"^\n?(#{1,2}|\\*{1,2}|[0-9]{1,3}\\.)$"

    If this regex is used quite a lot, you might want to cache the NSRegularExpression object to avoid compiling it everytime.

    Regexpal is very useful to test regular expressions.

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