Swift - 计算器 - 错误：'String'类型的值没有成员'Int'

Question

这是我的第一篇文章。我刚刚加入了stackoverflow。我正在为学校做计算器并遵循本教程（虽然我没有按照他的界面）： https://www.youtube.com/watch?v=NJHsdjH2HdY&nohtml5=False

但我认为swift自那时起已更新，我收到错误“类型'字符串'的值没有成员'Int'”

非常感谢任何帮助！

这是我的代码：

class ViewController: UIViewController {

    @IBOutlet weak var lblResult: UILabel!

    var result = Float()
    var currentNumber = Float()

    var currentOp = String()

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        currentOp = "="
        lblResult.text = ("\(result)")
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func btnNumberInput(sender: UIButton) {
        currentNumber = currentNumber * 10 + Float(sender.titleLabel!.text!.Int()!)
        lblResult.text = ("\(currentNumber)")

    }

    @IBAction func btnOperation(sender: UIButton) {

        switch currentOp {
            case "=":
                result = currentNumber
            case "+":
                result = result + currentNumber
            case "-":
                result = result - currentNumber
            case "*":
                result = result * currentNumber
            case "/":
                result = result / currentNumber
            default:
                print("error")

        }

        currentNumber = 0
        lblResult.text = ("\(result)")

        if(sender.titleLabel!.text == "=") {
            result = 0
        }

        currentOp = sender.titleLabel!.text! as String!
    }


    @IBAction func btnClear(sender: UIButton) {
        result = 0
        currentNumber = 0
        currentOp = "="
        lblResult.text = ("\(result)")
    }





}