RegExKitLite Expression Question - iphone

Question

I'm having trouble coming up with an RegExKitLite expression that will match. I'm parsing a string and I want it to grab everything till it comes upon the first occurrence of a colon
What would be the expression in RegExKitLite to do that?
Thanks!

Answer 1

This regex will match everything from the start until (but excluding) the first colon:
^[^:]*
To include the first colon is as simple as putting it on the end:
^[^:]*:
So, to use either of those with RegexKitLite, you can do:
NSString * firstItem = [someString stringByMatching:#"^[^:]*" capture:0];
Note how there is no parentheses - since * is greedy you can simply use the negated class and use captured group 0 (i.e. the whole match).
It's worth noting that most languages will include functions that allow you to do this with a regular function, for example ListFirst(MyString,':') or MyString.split(':')[0]
I suspect Objective-C has something similar to this ... yep, see here
NSString *string = #"oop:ack:bork:greeble:ponies";
NSArray *chunks = [string componentsSeparatedByString: #":"];

Answer 2

To do this specifically with RegexKitLite, you'll need to do the following:
Add the RegexKitLite.h/.m files to your project
Import RegexKitLite.h into the file where you need to use regular expressions
Use the following to grab the stuff before the colon:
NSString * everythingBeforeTheColon = [someString stringByMatching:#"([^:]*):" capture:1];

Answer 3

I just updated my SO answer here, so I figured I'd use that to benchmark the standard foundation componentsSeparatedByString: and RegexKitLites componentsSeparatedByRegex:. The line of code inside the for() loop for each was (essentially):
NSString *string = #"oop:ack:bork:greeble:ponies";
for() { NSArray *chunks = [string componentsSeparatedByString: #":"]; }
for() { NSArray *chunks = [string componentsSeparatedByRegex: #":"]; }
Times returned were (time is in microseconds per operation):
componentsSeparatedByString: 3.96810us
componentsSeparatedByRegex: 2.46155us
EDIT:
I thought I'd go one better: How to use RegexKitLite to create a NSArray of NSArrays from a string containing multiple lines of colon separated data (ie, /etc/passwd). Modified from the comma separated value example in the RegexKitLite documentation. When finished, the variable splitLinesArray contains the finished product.
NSString *theString = #"a:b:c\n1:2:3\nX:Y:Z\n"; // An example string to work on.
NSArray *linesArray = [theString componentsSeparatedByRegex:#"(?:\r\n|[\n\v\f\r\\x85\\p{Zl}\\p{Zp}])"];
id splitLines[[linesArray count]];
NSUInteger splitLinesIndex = 0UL;
for(NSString *lineString in linesArray) { splitLines[splitLinesIndex++] = [lineString componentsSeparatedByRegex:#":"]; }
NSArray *splitLinesArray = [NSArray arrayWithObjects:splitLines count:splitLinesIndex];