Validador IPv6 para cacau

O seguinte método Cocoa permitirá que você verifique um endereço IPv6:

- (BOOL)isIPv6:(NSString *)candidate
{
    /*
     fe80:0000:0000:0000:0204:61ff:fe9d:f156        // full form of IPv6
     fe80:0:0:0:204:61ff:fe9d:f156                  // drop leading zeroes
     fe80::204:61ff:fe9d:f156                       // collapse multiple zeroes to :: in the IPv6 address
     fe80:0000:0000:0000:0204:61ff:254.157.241.86   // IPv4 dotted quad at the end
     fe80:0:0:0:0204:61ff:254.157.241.86            // drop leading zeroes, IPv4 dotted quad at the end
     fe80::204:61ff:254.157.241.86                  // dotted quad at the end, multiple zeroes collapsed

     In addition, the regular expression matches these IPv6 forms:

     ::1        // localhost
     fe80::     // link-local prefix
     2001::     // global unicast prefix
     */

    NSString *regex = @"^\s*((([0-9A-Fa-f]{1,4}:){7}([0-9A-Fa-f]{1,4}|:))|(([0-9A-Fa-f]{1,4}:){6}(:[0-9A-Fa-f]{1,4}|((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){5}(((:[0-9A-Fa-f]{1,4}){1,2})|:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){4}(((:[0-9A-Fa-f]{1,4}){1,3})|((:[0-9A-Fa-f]{1,4})?:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){3}(((:[0-9A-Fa-f]{1,4}){1,4})|((:[0-9A-Fa-f]{1,4}){0,2}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){2}(((:[0-9A-Fa-f]{1,4}){1,5})|((:[0-9A-Fa-f]{1,4}){0,3}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){1}(((:[0-9A-Fa-f]{1,4}){1,6})|((:[0-9A-Fa-f]{1,4}){0,4}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(:(((:[0-9A-Fa-f]{1,4}){1,7})|((:[0-9A-Fa-f]{1,4}){0,5}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:)))\s*$";

    NSPredicate *test = [NSPredicate predicateWithFormat:@"SELF MATCHES[c] %@", regex];

    return [test evaluateWithObject:candidate];
}

Eu escrevi um teste de unidade verificando todos os casos mencionados acima e funciona muito bem.