Question

首先让我解释一下这个概念。我问用户3个问题，这些问题存储在NSArray中。用户将使用一个UITextField来写出问题的所有3个答案。

我希望发生这种情况，当数组中显示所有三个问题时，下次用户按下下一个UIButton时，它会转移到新的UIViewController。我在main.storyboard中创建了segue，并为其指定了countdownSegue的标识符。

当我运行我的应用程序时，我到达最后一个问题并按下“下一步”按钮，应用程序崩溃并且错误是＆＃34;致命错误：数组索引超出范围＆＃34; - 我不明白为什么。我的代码在下面显示我的问题数组和按下时我的按钮发生了什么。任何帮助非常感谢。

let questions = ["Where are you going?", "Which city?", "When do you go?"]

var currentQuestionIndex = 0

let placeholder = ["Country", "City", "Date"]

var currentPlaceholderIndex = 0

@IBAction func nextButton(sender: AnyObject) {

    // Initial setup on button press
    questionTextField.hidden = false
    barImage.hidden = false
    questionTextField.placeholder = placeholder[currentPlaceholderIndex]
    questionLabel.text = questions[currentQuestionIndex]
    questionTextField.resignFirstResponder()

    // Reset text field to have no text
    questionTextField.text = ""

    // Displays the questions in array and displays the placeholder text in the textfield
    if currentQuestionIndex < questions.count && currentPlaceholderIndex < placeholder.count {

        currentQuestionIndex++
        currentPlaceholderIndex++
        buttonLabel.setTitle("Next", forState: UIControlState.Normal)

    } else if currentQuestionIndex > questions.count && currentPlaceholderIndex > placeholder.count {

        performSegueWithIdentifier("countdownSegue", sender: self)

    }

}

谢谢！

Answer 1

您应该针对index检查count - 1，因为索引是从零开始的。

if currentQuestionIndex < questions.count - 1 && currentPlaceholderIndex < placeholder.count - 1{
    currentQuestionIndex++
    currentPlaceholderIndex++
    buttonLabel.setTitle("Next", forState: UIControlState.Normal)
} else {
    performSegueWithIdentifier("countdownSegue", sender: self)
}

修改

从阵列中获取值以显示文本时，您没有检查索引。当您点击上一个问题的“下一步”按钮时，它会溢出。

@IBAction func nextButton(sender: AnyObject) { // Initial setup on button press questionTextField.hidden = false barImage.hidden = false questionTextField.resignFirstResponder() // Reset text field to have no text questionTextField.text = "" // Displays the questions in array and displays the placeholder text in the textfield if currentQuestionIndex < questions.count && currentPlaceholderIndex < placeholder.count { questionTextField.placeholder = placeholder[currentPlaceholderIndex] questionLabel.text = questions[currentQuestionIndex] currentQuestionIndex++ currentPlaceholderIndex++ buttonLabel.setTitle("Next", forState: UIControlState.Normal) } else { performSegueWithIdentifier("countdownSegue", sender: self) } }

如何在数组计数结束时转换到新的UIViewController

1 个答案: