Swift extensions for String

StringExtensions

extension String {
    func scan(regex : String) -> [String] {
        let regex = NSRegularExpression(pattern: regex,
            options: nil, error: nil)!
        let nsString = self as NSString
        let results = regex.matchesInString(nsString as String,
            options: nil, range: NSMakeRange(0, nsString.length))
            as! [NSTextCheckingResult]
        return map(results) { nsString.substringWithRange($0.range)}
    }
    subscript (i: Int) -> Character {
        return self[advance(self.startIndex, i)]
    }
    
    subscript (i: Int) -> String {
        return String(self[i] as Character)
    }
    
    subscript (r: Range<Int>) -> String {
        return substringWithRange(Range(start: advance(startIndex, r.startIndex), end: advance(startIndex, r.endIndex)))
    }
}

let number = "(123) (456) 7890"
let wordArr = number.scan("\\w+")
println(wordArr) // [123, 456, 7890]

let digitsOnly = "".join(wordArr)
println(digitsOnly) // 1234567890

"abcde"[0] === "a"
"abcde"[0...2] === "abc"
"abcde"[2..<4] === "cd"