Question

我已经成功更新了文本字段的值，现在我正在尝试添加第二个步进器，但应用程序现在崩溃了。

    @IBOutlet weak var propertyTypeField: UITextField!
@IBOutlet weak var insuranceTypeField: UITextField!
@IBOutlet weak var bedroomField: UITextField!
@IBOutlet weak var bathroomField: UITextField!
@IBOutlet weak var doYouOwnPropertyField: UITextField!

@IBOutlet weak var propertyYearField: UITextField!
@IBOutlet weak var bathroomStepper: UIStepper!
@IBOutlet weak var bedroomStepper: UIStepper!

override func viewDidLoad() {
    super.viewDidLoad()

    view.backgroundColor = UIColor(red: 0xE1/255, green: 0xE1/255, blue: 0xE1/255, alpha: 1.0)


    //Bedroom stepper setup
    bedroomField.text = "\(Int(bedroomStepper.value))"
    bedroomStepper.addTarget(self, action: "stepperValueDidChange:", forControlEvents: .ValueChanged)

    //Bathroom stepper setup
    bathroomField.text = "\(Int(bathroomStepper.value))"
    bathroomStepper.addTarget(self, action: "stepperValueDidChange:", forControlEvents: .ValueChanged)

    // Do any additional setup after loading the view.
}




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

@IBAction func viewTapped(sender : AnyObject) {

    propertyTypeField.resignFirstResponder()
    insuranceTypeField.resignFirstResponder()
    bedroomField.resignFirstResponder()
    bathroomField.resignFirstResponder()
    doYouOwnPropertyField.resignFirstResponder()
    propertyYearField.resignFirstResponder()

}

func stepperValueDidChange(stepper: UIStepper) {

    let bedroomStepperMapping: [UIStepper: UITextField] = [bedroomStepper: bedroomField]
    if !(bedroomField.text == ""){
    bedroomStepperMapping[stepper]!.text = "\(Int(stepper.value))"}

    let bathroomStepperMapping: [UIStepper: UITextField] = [bathroomStepper: bathroomField]
    if !(bathroomField.text == ""){
    bathroomStepperMapping[stepper]!.text = "\(Int(stepper.value))"}
}

这是我正在使用的整个代码。

我得到的错误是

致命错误：在解包可选值时意外发现nil

希望有人可以提供帮助。

由于

Answer 1

通过使用! bedroomStepperMapping[stepper]!.text告诉编译器，那里会有一个值。因为没有人显然你得到错误。在打开它之前检查值是否为零

要检查行中是否为nil

if !(bedroomField.text == ""){ 

    //Ok to unwrap object
 }

Answer 2

如果您正在使用可选值，那么首先检查值是否存在，如果不存在那么必须不是b null所以这样做

if let bedFeild = Int(stepper.value) {
bedroomStepperMapping[stepper].text = bedFeild
}

现在，如果值存在则不会崩溃，那么将为其分配值，否则不会发生任何崩溃

Answer 3

func stepperValueDidChange(stepper: UIStepper) {
    if bedroomStepper == stepper{
        bedroomField.text = "\(Int(stepper.value))"}
    if  bathroomStepper == stepper{
        bathroomField.text = "\(Int(stepper.value))"}
    }
}

添加第二个步进器时应用程序崩溃

3 个答案: