Regular Expressions in Objective-C

This class allows you to use very powerfull regular expressions (because it’s based on regexec from C) in an object oriented way.
Thanks to the post of David Teare, I finally find a very easy and powerfull solution for using regular expressions in Objective-C. David’s code only returns a boolean to indicate if the NSString was matching the given regular expression. I improve its method by returning a NSMutableArray with the different sub-expressions that lead to a match. Unfortunately I wasn’t able to return nil when the sub-expression doesn’t produce a match, instead I return the empty NSString @””.

Download Regular Expression Source Code

[Updated the 16.05.2007] Thanks to everybody for you remarks, I updated the source file accordingly. I also add a example script to demonstrate the use of the method.

Download Regular Expression Source Code version 1.1

[Updated the 01.01.2008] After receiving a reader’s mail about the code’s licencing, I clarify the situation and add the GPL licence in the header as well as the full licence in the package.

Download Regular Expression Source Code version 1.1

[Update 22.02.2009] Hey I just discovered that TwitterFon, YMail and swisssms are using this class. Cool isn’t it.

[Updated the 08.04.2009] Bugfix the behavior when working on NSString with UTF8 encoded chars. Thanks to Ian Atha & soniccat for the correction

Download Regular Expression Source Code version 1.2

This entry was posted on Wednesday, December 27th, 2006 at 8:19 pm and is filed under Objective-C, Programmation. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

soniccat

Excellent library, but when i use multi-byte character ( russian in my example ) function crash. That happen because pmatch[i].rm_eo store a number of byte in string. In my example russian character have 2 byte and in
self substringToIndex:pmatch[i].rm_eo

i have out of range exception because pmatch[i].rm_eo > [self length]
I write that for resolved that problem:

size_t buffSize = pmatch[i].rm_eo - pmatch[i].rm_so + 1;
char* buff = (char*)malloc( buffSize );
memset(buff,0,sizeof(char)*buffSize );
memcpy(buff,[self UTF8String]+pmatch[i].rm_so, pmatch[i].rm_eo - pmatch[i].rm_so );

[substring addObject: [NSString stringWithUTF8String:buff] ];
free( buff );
Dmitry Chestnykh

BTW, you can add NSNull for empty substrings, but I agree that @"" is better.
Dmitry Chestnykh

Thanks!

There's a bug:

if (0 == regcomp(&re, regex, REG_EXTENDED)) {

should be

if (0 == regcomp(&re, [regex UTF8String], REG_EXTENDED)) {

(You definitely need to turn on "Stop on all warnings" compile option ;)

Also, you have "false" instead of "NO" in the beginning.

Anyway, thanks for the code!
Gavin

Hey Well done, however I cannot work out how to get the results, do you have an example on how to get the returned array ?
David Teare

Hey, cool! I'm glad my code sample helped you out.

I was amazed that Cocoa/objective C didn't have an easier way to do regex; I guess I have been spoiled by Ruby and its =~ operator :)