空陣列導致我的應用程序在Swift崩潰

Question

我經常遇到這個錯誤「致命錯誤：索引超出範圍」，經過研究後，我仍然不確定如何解決這個問題。爲了給出上下文，我已經開始使用空數組var playersArray = [UITextField]()，以便用戶可以輸入他們的名字來玩遊戲。然後我要確保用戶擁有或如果玩家已經進入了一個值到該文本框，然後生病追加該值數組還沒有進入一個值的文本字段每個名稱插槽

if let player1Name = name1.text, !player1Name.isEmpty 
     { playersArray.append(name1) 

     } else { 
      print("Player 1 Empty") 

。 我遇到的問題是，如果我運行遊戲，並且沒有用戶輸入任何10個文本字段的名稱，則遊戲將崩潰。我假設這是因爲數組是空的？

的錯誤出現在這條線，我隨機用於遊戲元素的數組中的數名：

let RandomPlayer = playersArray[Int(arc4random_uniform(UInt32(playersArray.count)))] 

我認爲如果數組爲空，則.count將無法​​正常工作？

如何確保遊戲不會崩潰，如果數組是空的？

CODE：

var playersArray = [UITextField]() 

    override func viewDidLoad() { 
     super.viewDidLoad() 
     textColor() 
     question1View.isHidden = true 
     questionLabel.transform = CGAffineTransform(rotationAngle: CGFloat.pi/2) 


    } 

    override func didReceiveMemoryWarning() { 
     super.didReceiveMemoryWarning() 
    } 

    // Alert message on startup 
    func alertMessageOnStartUp(){ 
     let alert = UIAlertController(title: "Warning!", message: "Please drink responsibly. By continuing, you agree that you are responsible for any consequences that may result from BottomsUp.", preferredStyle: UIAlertControllerStyle.alert) 
     alert.addAction(UIAlertAction(title: "Agree", style: UIAlertActionStyle.default, handler: nil)) 
     self.present(alert, animated: true, completion: nil) 
    } 

    // Dismiss keyboard when tapped outside the keyboard 
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) { 
     self.view.endEditing(true) 
    } 

    // Dimiss keybaord when return button is tapped 
    func textFieldShouldReturn(_ textField: UITextField) -> Bool { 
     name1.resignFirstResponder() 
     name2.resignFirstResponder() 
     name3.resignFirstResponder() 
     name4.resignFirstResponder() 
     name5.resignFirstResponder() 
     name6.resignFirstResponder() 
     name7.resignFirstResponder() 
     name8.resignFirstResponder() 
     name9.resignFirstResponder() 
     name10.resignFirstResponder() 
     return(true) 
    } 

    //randomise background colour of each question page 
    func getRandomBackgroundColor() -> UIColor{ 
     let randomRed:CGFloat = CGFloat(drand48()) 
     let randomGreen:CGFloat = CGFloat(drand48()) 
     let randomBlue:CGFloat = CGFloat(drand48()) 
     return UIColor(red: randomRed, green: randomGreen, blue: randomBlue, alpha: 1.0) 
    } 

     func textColor(){ 
     name1.textColor = UIColor.white 
     name2.textColor = UIColor.white 
     name3.textColor = UIColor.white 
     name4.textColor = UIColor.white 
     name5.textColor = UIColor.white 
     name6.textColor = UIColor.white 
     name7.textColor = UIColor.white 
     name8.textColor = UIColor.white 
     name9.textColor = UIColor.white 
     name10.textColor = UIColor.white 
    } 

    @IBAction func playButton(_ sender: Any) { 
     alertMessageOnStartUp() 

     if let player1Name = name1.text, !player1Name.isEmpty 
     { playersArray.append(name1) 

     } else { 
      print("Player 1 Empty") 
     } 

     if let player2Name = name2.text, !player2Name.isEmpty 
     { playersArray.append(name2) 

     } else { 
      print("Player 2 Empty") 
     } 

     if let player3Name = name3.text, !player3Name.isEmpty 
     { playersArray.append(name3) 

     } else { 
      print("Player 3 Empty") 
     } 

     if let player4Name = name4.text, !player4Name.isEmpty 
     { playersArray.append(name4) 

     } else { 
      print("Player 4 Empty") 
     } 

     if let player5Name = name5.text, !player5Name.isEmpty 
     { playersArray.append(name5) 

     } else { 
      print("Player 5 Empty") 
     } 

     if let player6Name = name6.text, !player6Name.isEmpty 
     { playersArray.append(name6) 

     } else { 
      print("Player 6 Empty") 
     } 

     if let player7Name = name7.text, !player7Name.isEmpty 
     { playersArray.append(name7) 

     } else { 
      print("Player 7 Empty") 
     } 

     if let player8Name = name8.text, !player8Name.isEmpty 
     { playersArray.append(name8) 

     } else { 
      print("Player 8 Empty") 
     } 

     if let player9Name = name9.text, !player9Name.isEmpty 
     { playersArray.append(name9) 

     } else { 
      print("Player 9 Empty") 
     } 

     if let player10Name = name10.text, !player10Name.isEmpty 
     { playersArray.append(name10) 

     } else { 
      print("Player 10 Empty") 
     } 

     question1View.isHidden = false 
     question1View.backgroundColor = getRandomBackgroundColor() 


     let RandomPlayer = playersArray[Int(arc4random_uniform(UInt32(playersArray.count)))] 
     let RandomQuestion = questionArray[Int(arc4random_uniform(UInt32(questionArray.count)))] 
     questionLabel.text = RandomPlayer.text! + RandomQuestion 

    } 

    @IBAction func nextQuestionButton(_ sender: Any) { 
     question1View.backgroundColor = getRandomBackgroundColor() 

     let RandomPlayer = playersArray[Int(arc4random_uniform(UInt32(playersArray.count)))] 
     let RandomQuestion = questionArray[Int(arc4random_uniform(UInt32(questionArray.count)))] 
     questionLabel.text = RandomPlayer.text! + RandomQuestion 
    } 
} 

Answer 1

打破下來：

Int(arc4random_uniform(UInt32(playersArray.count))) 

這條線得到一個隨機數爲0的最小值和playersArray的長度減去1

的最大值實際上，我不知道當你傳入的參數是0時，它做了什麼，但它並不重要，我們將在下面看到。

然後你使用它在這裏隨機值：

playersArray[thatRandomNumber] 

因爲在playersArray沒有元素，無論價值是thatRandomNumber什麼，這將是出界。

你可能想要更多的東西是這樣的：

let RandomPlayer = <some default value> 
if !playersArray.isEmpty { 
    RandomPlayer = playersArray[Int(arc4random_uniform(UInt32(playersArray.count)))] 
} 

編輯

你最新的代碼似乎仍然沒有做任何事情來阻止索引到空數組。

您有：

@IBAction func playButton(_ sender: Any) { 
    ... 
    let RandomPlayer = playersArray[Int(arc4random_uniform(UInt32(playersArray.count)))] 
    let RandomQuestion = questionArray[Int(arc4random_uniform(UInt32(questionArray.count)))] 
    questionLabel.text = RandomPlayer.text! + RandomQuestion 
} 

您需要：

@IBAction func playButton(_ sender: Any) { 
    ... 
    if playersArray.isEmpty { 
     // do something about that 
    } else { 
     let RandomPlayer = playersArray[Int(arc4random_uniform(UInt32(playersArray.count)))] 
     let RandomQuestion = questionArray[Int(arc4random_uniform(UInt32(questionArray.count)))] 
     questionLabel.text = RandomPlayer.text! + RandomQuestion 
    } 
} 

Answer 2

playersArray.count爲空數組是0，所以你是在試圖訪問playersArray [0] - 但數組是空的，所以沒有什麼在0指數存在。

你應該做這樣的事情：

let randomPlayer: Player 
if !playersArray.isEmpty { 
    randomPlayer = playersArray[Int(arc4random_uniform(UInt32(playersArray.count)))] 
} else { 
    randomPlayer = Player() //create a fallback player 
} 

或者你可以把randomPlayer可選的，而不是提供一個備用的值。取決於您對該變量的需求。