is alpha?

swift-isAplha.swift

func isAlpha(char: Character) -> Bool {
    switch char {
    case "a"..."z":
        return true
    case "A"..."Z":
        return true
    default:
        return false
    }
}

func isAlpha2(char: String) -> Bool {
    return charset(NSCharacterSet.alphanumericCharacterSet(), containsCharacter: char)
}

func charset(cset:NSCharacterSet, containsCharacter s:String) -> Bool {
    let ix = s.startIndex
    let ix2 = s.endIndex
    let result = s.rangeOfCharacterFromSet(cset, options: [], range: ix..<ix2)
    return result != nil
}

func isAlpha3(char: String) -> Bool {
    let regex = try! NSRegularExpression(pattern: "[:alpha:]", options: [])
    return regex.firstMatchInString(char, options: [], range: NSMakeRange(0, char.characters.count)) != nil
}


isAlpha("a")
isAlpha("B")
isAlpha(" ")

isAlpha2("a")
isAlpha2("B")
isAlpha2("?")

isAlpha3("a")
isAlpha3("B")
isAlpha3("?")