Swift #5 animateWithDuration
@IBOutlet weak var mainLabel: UILabel!

func initUI(){
    var message:String = getMessage(message:"いあうえ",message2:"390u8")
    println(message)
        
    message = getMessage(message2:"むぎちゃ")
    println(message)

    UIView.animateWithDuration(
        2.0,
        delay: 1.0,
        usingSpringWithDamping: 1.0,
        initialSpringVelocity: 0.0,
        options: UIViewAnimationOptions.CurveEaseInOut,
        animations:{()in
            self.mainLabel.frame = CGRectMake(100.0, 300.0, self.mainLabel.frame.size.width, self.mainLabel.frame.size.height)
        },
        completion:{(finished)in
            println("finished:\(finished)")
            
        })
}
func getMessage(var message:String="ABC",var message2:String="MBNRKF")->String{
    return "\(message) \(message2)"
}

override func viewDidLoad() {
    super.viewDidLoad()
    initUI()
}

出力結果
いあうえ 390u8
ABC むぎちゃ
finished:true