Question

I have been struggling with using NSRegularExpression, is there some major difference from Regex that I am unaware of?

I am trying this:

NSString *str = @"&url=http%3A%2F%2Fi.hello.com/random/depeth/in/string.JPG%3Fset_id"

NSError *error = NULL;

NSRegularExpression *regex = [NSRegularExpression 
                              regularExpressionWithPattern:@"i(.+?)%3Fset_id" 
                              options:NSRegularExpressionCaseInsensitive 
                              error:&error];

NSRange rangeOfFirstMatch = [regex rangeOfFirstMatchInString:str 
                             options:0 range:NSMakeRange(0, [str length])];

I would like rangeOfFirstMatch to be the range of .hello.com/random/depeth/in/string.JPG

regex “i(.+?)%3Fset_id” seems to work fine in preg.

Kind of lost.

Thanks in advance.

Answer 1

rangeOfFirstMatchInString:… doesn’t do what you’re expecting: It finds the first match in the string of the entire regex. What you want is something like:

NSTextCheckingResult *result = [regex firstMatchInString:Str options:0 range:NSMakeRange(0, [Str length])];
NSRange rangeOfFirstSubexpression = [result rangeAtIndex:1];
NSString *firstSubexpression = [Str substringWithRange:rangeOfFirstSubexpression];

(Also note that capitalizing non-global non-constants isn’t Cocoa convention, though that obviously won’t break your code.)