我申请系统安全主题的报告。 Caesar 的 swift 代码。我在解密阶段遇到了问题。
当我输入 key 时,程序随机排除错误:
Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value
或者数组退出错误
我是新手。请向我解释如何修复此错误并使我的程序正常运行。
Google 没有帮助我。
import UIKit
class CaesarCipher: UIViewController {
@IBOutlet weak var messageText: UITextField!
@IBOutlet weak var keyText: UITextField!
@IBOutlet weak var cipherTextLabel: UILabel!
////////////////////////////////////////////////////////////////////////////
@IBOutlet weak var cryptMessageText: UITextField!
@IBOutlet weak var cryptKeyText: UITextField!
@IBOutlet weak var decryptTextLabel: UILabel!
@IBAction func cipherButton(_ sender: Any) {
if (messageText.text == "") || (keyText.text == "")
{
let alert = UIAlertController(title: "Ошибка", message: "Одно, или несколько полей пустые", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "Ок", style: .default, handler: nil))
self.present(alert, animated: true)
}
else
{
let key = keyText.text
let e: Int32 = Int32.init(key!)!
//let upKey: Int32 = Int32.init(&e)
let messageCipher = messageText.text
// var i: Int8 = Int8.init(messageCipher!)!
//let up: UnsafeMutablePointer<Int8> = UnsafeMutablePointer<Int8>.init(&i)
//cipherTextLabel = encrypt(up, e)
let encryptText = cipher(messageCipher!, shift: Int(e))
cipherTextLabel.text = "\(encryptText)"
}
}
//////////////////////////////////////////////////////////////////////////////////////////////
@IBAction func decryptButton(_ sender: Any) {
if (cryptMessageText.text == "") || (cryptKeyText.text == "")
{
let alert = UIAlertController(title: "Ошибка", message: "Одно, или несколько полей пустые", preferredStyle: .alert)
alert.addAction(UIAlertAction(title: "Ок", style: .default, handler: nil))
self.present(alert, animated: true)
}
else
{
let cryptKey = cryptKeyText.text
let e: Int = Int.init(cryptKey!)!
//let upKey: Int32 = Int32.init(&e)
let decryptMessageText = cryptMessageText.text
// var i: Int8 = Int8.init(messageCipher!)!
//let up: UnsafeMutablePointer<Int8> = UnsafeMutablePointer<Int8>.init(&i)
//cipherTextLabel = encrypt(up, e)
let decryptText = decipher(decryptMessageText!, shift2: Int(e))
decryptTextLabel.text = "\(decryptText)"
}
}
override func viewDidLoad() {
super.viewDidLoad()
self.hideKeyboard()
}
}
func cipher( _ text:String, shift:Int ) -> String {
var textCharArray:[Character] = Array( text.characters )
let alphabet = Array("0123456789abcdefghijklmnopqrstuvxyzABCDEFGHIJKLMNOPQRSTUWVXYZ !".characters);
let offset = alphabet.count // alphabet.length in other languages
for i in 0 ..< text.characters.count {
let oldChar = textCharArray[ i ]
let oldCharIdx = alphabet.index( of:oldChar ) // get index of
let oldCharIdxUnwrapped = oldCharIdx // oldCharIdx can be null!
let newCharIdx = ( oldCharIdxUnwrapped! + shift + offset ) % offset
let newChar = alphabet[ newCharIdx ]
textCharArray[ i ] = newChar
}
return String( textCharArray )
}
func decipher( _ text:String, shift2:Int ) -> String {
// when calling a function you don't have to specify the first argument...
// For other arguments you have to specify it!
return cipher( text, shift:shift2 * -1 )
}
最佳答案
当存在可选值(可能为 nil 的值)并且您尝试解开它(使用“!”)时,通常会引发您看到的错误。
Swift also introduces optional types, which handle the absence of a value. Optionals say either “there is a value, and it equals x” or “there isn’t a value at all”.
话虽这么说,这里的问题是 UITextfields 当“空”时其文本属性可能为 nil。所以当你这样做时
let key = keyText.text
let e: Int32 = Int32.init(key!)!
key
可以是零值。并且(nil)!
将导致Unexpectedfound nil while unwrapping anOptional value
。
要解决此问题,我建议您为 UITextfield 的文本属性添加 nil 检查,或者
将 if else
block 更改为以下内容
if let key = keyText.text, let messageCipher = messageText.text, !key.isEmpty, !messageCipher.isEmpty {
// key and messageCipher are neither nil nor empty.
} else {
// keyText.text or messageText.text are either nil or empty
}
如果您对 swift 编程和制作 iOS 应用程序感兴趣,我建议您详细了解 swift 如何处理 可选
以及隐式解包的可选内容。一个起点是 https://docs.swift.org/swift-book/LanguageGuide/TheBasics.html并跟进教程。
关于ios - 凯撒密码在 Swift 上解密时出错,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/54722360/