Split String into groups with specific length

Question

How can I split the given String in Swift into groups with given length, reading from right to left?

For example, I have string 123456789 a

Answer 1

Here is a version using NSRegularExpressions

func splitedString(string: String, length: Int) -> [String] {
    var groups = [String]()
    let regexString = "(\\d{1,\(length)})"
    do {
        let regex = try NSRegularExpression(pattern: regexString, options: .CaseInsensitive)
        let matches = regex.matchesInString(string, options: .ReportCompletion, range: NSMakeRange(0, string.characters.count))
        let nsstring = string as NSString
        matches.forEach {
            let group = nsstring.substringWithRange($0.range) as String
            groups.append(group)
        }
    } catch let error as NSError {
        print("Bad Regex Format = \(error)")
    }

    return groups
}