[swift] swift make a app to call

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var labelTop: UILabel!

    @IBOutlet weak var labelDown: UILabel!

    override func viewDidLoad() {

        super.viewDidLoad()

        // Do any additional setup after loading the view, typically from a nib.

    }

    override func didReceiveMemoryWarning() {

        super.didReceiveMemoryWarning()

        // Dispose of any resources that can be recreated.

    }

    @IBAction func numberClick(sender: UIButton) {

        labelTop.text = labelTop.text! + sender.currentTitle!

    }

    @IBAction func clearClick(sender: UIButton) {

        labelTop.text = ""

        labelDown.text = ""

    }

    @IBAction func submitClick(sender: UIButton) {

        //labelTop.text?.characters.count

        

        if labelTop.text?.lengthOfBytesUsingEncoding(NSUTF8StringEncoding) == 10 {

            labelDown.text = "撥打電話:" + labelTop.text!

        }else{

            labelDown.text = "長度不足10"

        }

    }

}