How to write regular expressions in Objective C (NSRegularExpression)?

Question

I have this regex working when I test it in PHP but it doesn\'t work in Objective C:

(?:www\\.)?((?!-)[a-zA-Z0-9-]{2,63}(?

        

Answer 1

A NSTextCheckingResult has multiple items obtained by indexing into it.

[match rangeAtIndex:0]; is the full match.
[match rangeAtIndex:1]; (if it exists) is the first capture group match.
etc.

You can use something like this:

NSString *searchedString = @"domain-name.tld.tld2";
NSRange   searchedRange = NSMakeRange(0, [searchedString length]);
NSString *pattern = @"(?:www\\.)?((?!-)[a-zA-Z0-9-]{2,63}(?

NSLog output:

match: domain-name.tld.tld2
domain-name
tld.tld2

Do test that the match ranges are valid.

More simply in this case:

NSString *searchedString = @"domain-name.tld.tld2";
NSRange   searchedRange = NSMakeRange(0, [searchedString length]);
NSString *pattern = @"(?:www\\.)?((?!-)[a-zA-Z0-9-]{2,63}(?

Swift 3.0:

let searchedString = "domain-name.tld.tld2"
let nsSearchedString = searchedString as NSString
let searchedRange = NSMakeRange(0, searchedString.characters.count)
let pattern = "(?:www\\.)?((?!-)[a-zA-Z0-9-]{2,63}(?

print output:

match: domain-name.tld.tld2
matchText1: domain-name
matchText2: tld.tld2

More simply in this case:

do {
    let regex = try NSRegularExpression(pattern:pattern, options: [])
    let match = regex.firstMatch(in:searchedString, options:[], range:searchedRange)

    let matchText1 = nsSearchedString.substring(with: match!.rangeAt(1))
    print("matchText1: \(matchText1)")

    let matchText2 = nsSearchedString.substring(with: match!.rangeAt(2))
    print("matchText2: \(matchText2)")

} catch let error as NSError {
    print(error.localizedDescription)
}

print output:

matchText1: domain-name
matchText2: tld.tld2