Question

我确定字符串不是nil并且标签存在，我试图找出标签中的文本为零的原因。 destinationViewController的其他成员设置正确，但只要我添加行来设置标签，程序就会崩溃。

// Mark segue
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    // Get reference to the destination view controller
    var detailVC = segue.destinationViewController as! DetailViewController
    var detailImages: Array<UIImage> = []
    detailImages.append(UIImage(named: "pup.jpg")!)
    detailImages.append(UIImage(named: "dog.png")!)
    // Set the property to the selected location so when the view for
    // detail view controller loads, it can access that property to get the feeditem obj
    detailVC.selectedLocation = _selectedLocation;
    println(_str!)
    detailVC.myLabel.text = "hello"
}

Answer 1

这是因为myLabel的出口不会在prepareForSegue中设置，因此它将为零。请尝试以下方法，

在DetailViewController中创建一个字符串var，

var labelText: String?

prepareForSegue

中的

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    // Get reference to the destination view controller
    var detailVC = segue.destinationViewController as! DetailViewController
    var detailImages: Array<UIImage> = []
    detailImages.append(UIImage(named: "pup.jpg")!)
    detailImages.append(UIImage(named: "dog.png")!)
    // Set the property to the selected location so when the view for
    // detail view controller loads, it can access that property to get the feeditem obj
    detailVC.selectedLocation = _selectedLocation;
    println(_str!)
    detailVC.labelText = "hello"
}

并在DetailViewController

的viewDidLoad中

override func viewDidLoad() {
    super.viewDidLoad()

    self.myLabel.text = labelText
    // Do any additional setup after loading the view.
}

Answer 2

是的，最后我将prepareForSegue中的最后一行更改为

detailVC.myString = _str as? String

我不确定我是不是？因为在我的detailVC中我添加了：

var myString:String?

将NSString转换为String的最佳位置在哪里，或者无关紧要？谢谢！

在prepareForSegue中设置destinationviewcontroller的标签文本会引发错误：在解包时意外发现nil可选值

2 个答案: