swift - 类型 'string' 的值没有成员 'text'

Question

我的应用程序的一部分是从 fextfiled 和 Double in 10 中获取一个数字。我收到此错误消息:

警报消息是关于此处代码的第 2 句。

class ViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {

    @IBOutlet var label: UILabel!
    @IBOutlet var Picker1: UIPickerView!
    @IBOutlet var num: UITextField!

    var array1 = ["km","m","dm","mm"]
    var PlaceAnswer = 0
    var answer = Float()
   override func viewDidLoad() {
        super.viewDidLoad()   
    }
     override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
       }

    func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {

       return array1[row]

    }

    func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int{

        return array1.count
    }

     func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int{
        return 1
    }
    @IBAction func Submit(sender: AnyObject) {

        if(PlaceAnswer==0){
answer = num.text
            label.text = ("\(answer)")

        }

Answer 1

NSNumberFormatter 可以将 String 转换为 NSNumber:

let numberFormatter = NSNumberFormatter()
numberFormatter.numberStyle = .DecimalStyle
let number = numberFormatter.numberFromString(num.text)!
answer = number.floatValue