本文介绍了无法打开'Optional.None'的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
遇到错误致命错误时:
跟踪这个并不容易。导致此错误的原因是什么?
It is not that easy to trace this. What causes this error?
import UIKit
class WelcomeViewController: UIViewController {
let cornerRad:CGFloat = 10.0
@IBOutlet var label:UILabel
@IBOutlet var lvl1:UIButton
@IBOutlet var lvl2:UIButton
@IBOutlet var lvl3:UIButton
init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?) {
super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
}
override func viewDidLoad() {
super.viewDidLoad()
lvl1.layer.cornerRadius = cornerRad
lvl2.layer.cornerRadius = cornerRad
lvl3.layer.cornerRadius = cornerRad
}
}
推荐答案
您收到此错误,因为您尝试访问没有值的可选
变量。
示例:
You get this error, because you try to access a optional
variable, which has no value.Example:
// This String is an optional, which is created as nil.
var optional: String?
var myString = optional! // Error. Optional.None
optional = "Value"
if optional {
var myString = optional! // Safe to unwrap.
}
您可以阅读更多关于期权的信息
在官方。
You can read more about optionals
in the official Swift language guide.
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