class ViewController: UIViewController {

    @IBOutlet weak var edadGatoTextField: UITextField!
    @IBOutlet weak var mensajeLabel: UILabel!
    @IBOutlet weak var imagenGatoImageView: UIImageView!

    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 calcularEdadButtonPressed(sender: AnyObject) {

        var age = edadGatoTextField.text.toInt()

        // *** Bellow is the error! I'm trying to figure out if user
        // has not entered any number in order to display the message.

        if age {

            age = age * 7

            mensajeLabel.text = "Your cat's age is (age) years!"
            mensajeLabel.textColor = UIColor.blueColor()

            edadGatoTextField.resignFirstResponder()

            imagenGatoImageView.image = UIImage(named: "cat2.jpg")

        } else {

            mensajeLabel.text = "Please enter a number!"
            mensajeLabel.textColor = UIColor.redColor()

        }

    }

}