Question

这是我在Xcode项目中的数组。

Var questions = ["q.1", "q.2", "q.3"]

我添加了两个按钮，即前进按钮和后退按钮，以滚动查看问题。现在，当我在模拟器上启动项目时，我第一次点击后退按钮，这样它就直接将我带到“q.3”，它给了我一个错误说：

"Index out of range."

请记住，当我点击前进按钮时，它工作正常并带我“q.2”但是当我最初点击后退按钮时它给我一个错误。以下是我的代码。

@IBOutlet weak var question: UILabel! //this is my question label 
questions = ["q.1", "q.2", "q.3"] //this is my array of questions

currentQuestionIndex = 0

@IBAction func backwardBtnTapped(_ sender: Any) {

currentQuestionIndex -= 1
let noOfQuestions = questions.count
let previousQuestionIndex = currentQuestionIndex % noOfQuestions
question.text = questions[previousQuestionIndex]

@IBAction func forwardBtnTapped(_ sender: Any) {

currentQuestionIndex += 1
let noOfQuestions =  questions.count
let nextQuestionIndex =  currentQuestionIndex % noOfQuestions
question.text =  questions[nextQuestionIndex]

Answer 1

如果您希望分别在上一个和第一个问题时禁用前进和后退按钮。您可以执行以下操作：

假设您的按钮的出口名为forwardButton＆amp; backwardButton将其初始化为：

backwardButton.userInteractionEnabled = NO

将前向和后向按钮的IBAction设为：

@IBAction func backwardBtnTapped(_ sender: Any) {

    currentQuestionIndex -= 1
    if currentQuestionIndex == 0 {
        backwardButton.userInteractionEnabled = NO
    }
    forwardButton.userInteractionEnabled = YES
    let noOfQuestions = questions.count
    let previousQuestionIndex = currentQuestionIndex % noOfQuestions
    question.text = questions[previousQuestionIndex]
}

@IBAction func forwardBtnTapped(_ sender: Any) {

    currentQuestionIndex += 1
    if currentQuestionIndex >= questions.count - 1 {
        forwardButton.userInteractionEnabled = NO
    }
    backwardButton.userInteractionEnabled = YES
    let noOfQuestions =  questions.count
    let nextQuestionIndex =  currentQuestionIndex % noOfQuestions
    question.text =  questions[nextQuestionIndex] 
}

或者如果你想让它像现在这样做，只需在IBAction中为前进和后退按钮执行此操作：

@IBAction func backwardBtnTapped(_ sender: Any) {

    currentQuestionIndex -= 1
    if currentQuestionIndex < 0 {
        currentQuestionIndex = questions.count - 1
    }
    question.text = questions[currentQuestionIndex]
}

@IBAction func forwardBtnTapped(_ sender: Any) {

    currentQuestionIndex += 1
    if currentQuestionIndex >= questions.count {
        currentQuestionIndex = 0
    }
    question.text =  questions[currentQuestionIndex] 
}

Answer 2

尝试相似这可能有用

@IBAction func backwardBtnTapped(_ sender: Any) {

       currentQuestionIndex -= 1
       if currentQuestionIndex < 0
       {
          currentQuestionIndex = questions.count-1
       }
       question.text = questions[currentQuestionIndex]
    }

@IBAction func forwardBtnTapped(_ sender: Any) {

    currentQuestionIndex += 1
    if currentQuestionIndex >= questions.count
    {
       currentQuestionIndex = 0
    }
    question.text =  questions[currentQuestionIndex]
}

Answer 3

您需要检查条件。

if currentQuestionIndex > 0{
    let noOfQuestions = questions.count
    let previousQuestionIndex = currentQuestionIndex % noOfQuestions
    question.text = questions[previousQuestionIndex]
  }

尝试直接转到数组末尾时索引超出范围错误

3 个答案: