why my codes wrong? I need in calculator to make % what can I do for it?

//  ViewController.swift

//  calculator

//

//  Created by shoto chinchaladze on 12/13/16.

//  Copyright © 2016 shoto chinchaladze. All rights reserved.

//



import UIKit



class ViewController: UIViewController {



    //MARK: - IBOutlets

    @IBOutlet var firstNum: UITextField!

    @IBOutlet var math: UITextField!

    @IBOutlet var secondNum: UITextField!

    @IBOutlet var myLabel: 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.

    }

    // MARK: - IBAction

    @IBAction func calculate(sender: UIButton){

        let firstValue = Float(firstNum.text!)!

        let secondValue = Float(secondNum.text!)!

        let mathValue = math.text!

        var result = Float(0.0)



        //MARK: - switch

        switch mathValue {

        case "+":

            result = firstValue + secondValue

        case "-":

            result = firstValue - secondValue

        case "*":

            result = firstValue * secondValue

        case "/":

            result = firstValue / secondValue

        case "%":

            result = firstValue % secondValue

        default:

            break

        }

        myLabel.text = "\(result)"



    }



}