准备继续查看控制器时出现致命错误 [英] fatal error when prepared to segue to view controller
问题描述
我目前在 destViewController.titleLabel.text = "Testing Segue" 处解开可选值时遇到意外发现 nil 的致命错误.
I'm currently getting a fatal error unexpectedly found nil while unwrapping an optional value at destViewController.titleLabel.text = "Testing Segue".
我如何修复它,因为它在转到 SecondViewController 时出现错误?如何避免在 titleLabel.text 处变为 nil?
How do I fixed it since it getting me a error when it segue to SecondViewController? How do I avoid getting nil at titleLabel.text?
class ViewController: UIViewController {
@IBAction func action(sender: AnyObject) {
let alertController: UIAlertController = UIAlertController (title: "Next Page", message: "", preferredStyle: .Alert)
let yesAction = UIAlertAction (title: "YES", style: .Default ) { action -> Void in self.performSegueWithIdentifier("test", sender: self)
}
alertController.addAction (yesAction)
self.presentViewController(alertController, animated: true, completion: nil)
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if (segue.identifier == "test") {
let destViewController : SecondViewController = segue.destinationViewController as SecondViewController
destViewController.titleLabel.text = "Testing Segue"
}
}
}
推荐答案
首先像这样更新 ViewController
中的代码:
First Of all Update your code in your ViewController
like this:
class ViewController: UIViewController {
@IBAction func action(sender: AnyObject) {
let alertController: UIAlertController = UIAlertController (title: "Next Page", message: "", preferredStyle: .Alert)
let yesAction = UIAlertAction (title: "YES", style: .Default ) { action -> Void in self.performSegueWithIdentifier("test", sender: self)
}
alertController.addAction (yesAction)
self.presentViewController(alertController, animated: true, completion: nil)
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if (segue.identifier == "test") {
let destViewController : SecondViewController = segue.destinationViewController as SecondViewController
destViewController.textlbl = "Testing Segue"
}
}
}
在那之后,我认为你不能用你的方式为 textLabel 赋值,所以在你的 SecondViewController
中以这种方式为该标签赋值:
After that I think you can not assingn value to textLabel with your way so assign value to that label this way in your SecondViewController
:
import UIKit
class SecondViewController: UIViewController {
@IBOutlet weak var titleLabel: UILabel!
var textlbl = String()
override func viewDidLoad() {
super.viewDidLoad()
self.titleLabel.text = textlbl
}
}
还有 HERE 我创建了一个示例项目供您参考.
And HERE I cerated a sample project for you for more reference.
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