Search-and-replace with Regexes in Objective-C.

gistfile1.m

NSError *err = nil;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"%%.*?%%" options:0 error:&err];
if (!regex) {
    [NSException raise:@"badRegularExpression"
                format:@"The regular expression was incorrectly constructed. Error was: %@", err];
}

[regex replaceMatchesInString:aMutableString options:0 range:NSMakeRange(0, newURL.length) withTemplate:@""];