Match the Second Time a Word is Found In Regex - objective-c

Question

I'm pretty new to Regex and I'm just trying to get my head around it. The string I am trying to search through is this:
100 ON 12C 12,41C High Cool OK 0
101 OFF 32C 04,93C Low Dry OK 1
102 ON 07C 08,27C High Dry OK 0
What I am trying to do is work out the part to find the part 32C from the string. If possible, would the code be able to be changed a little each time in order to find the Nth occurrence of the word in the String. If it makes any difference I am going to be using this code in an iPhone application and thus Objective-C.

Answer 1

Your example is line-oriented and of equal weight (at the same time) biased towards the beginning of the line in the string.
If your engine flavor does grouping, you should be able to specify an occurance quantifier that will get you a single exact answer, without the need to do arrays and such.
In both cases the answer is in capture buffer 1.
examples:
$occurance = "2";
---------
/(?:[^\n]*?(\d+C)[^\n]*.*?){$occurance}/s
---------
or
---------
/(?:^.*?(\d+C)[\S\s]*?){$occurance}/m
expanded:
/
(?:
[^\n]*?
( \d+C )
[^\n]* .*?
){2}
/xs
/
(?:
^ .*?
( \d+C )
[\S\s]*?
){2}
/xm

Answer 2

You could try something like the following. You will have to replace regex_pattern with your regular expression pattern. In your case, regex_pattern should be something like #"\\s\\d\\dC" (a whitespace character (\\s) followed by a digit (\\d) followed by a digit (\\d) followed an upper-case letter C.
You may also wish to remove the NSRegularExpressionCaseInsensitive option if you can be sure that the letter C will never be lower case.
NSError *error = nil;
NSString *regex_pattern = #"\\s\\d\\dC";
NSRegularExpression *regex =
[NSRegularExpression regularExpressionWithPattern:regex_pattern
options:(NSRegularExpressionCaseInsensitive |
NSRegularExpressionDotMatchesLineSeparators)
error:&error];
NSArray *arrayOfMatches = [regex matchesInString:myString
options:0
range:NSMakeRange(0, [myString length])];
// arrayOfMatches now contains an array of NSRanges;
// now, find and extract the 2nd match as an integer:
if ([arrayOfMatches count] >= 2) // be sure that there are at least 2 elements in the array
{
NSRange rangeOfSecondMatch = [arrayOfMatches objectAtIndex:1]; // remember that the array indices start at 0, not 1
NSString *secondMatchAsString = [myString substringWithRange:
NSMakeRange(rangeOfSecondMatch.location + 1, // + 1 to skip over the initial space
rangeOfSecondMatch.length - 2)] // - 2 because we ignore both the initial space and the final "C"
NSLog(#"secondMatchAsString = %#", secondMatchAsString);
int temperature = [secondMatchAsString intValue]; // should be 32 for your sample data
NSLog(#"temperature = %d", temperature);
}