szhernovoy

func macAddr(maxX : UInt32 = 0xff) -> String {
    var s = ""
    for n in 1...6 {
        let rnd = Int((Double(arc4random())/0x100000000) * Double(maxX))
        let srnd = String(format: "%02x:", rnd)
        s += srnd
    }
    return (s as NSString).substringToIndex(countElements(s)-1)
}

szhernovoy

func randomString(len:Int) -> String {
    let charSet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
    var c = Array(charSet)
    var s:String = ""
    for n in (1...10) {
        s.append(c[Int(arc4random()) % c.count])
    }
    return s
}