SwiftUI实现选择题仅加载新题目时打乱答题选项

你当前的问题在于每次用户选择答案后，视图状态变化触发重绘，而ForEach里直接调用shuffleAnswers()会导致每次重绘都重新打乱选项。要实现仅加载新题时打乱选项，需要把打乱后的选项存储为状态变量，只在切换题目时更新它。

修改步骤： #

1. 添加状态变量存储当前题目的打乱选项
   在你的View结构体中添加一个@State变量，用来保存当前题目的已打乱选项：

@State private var currentShuffledAnswers: [String] = []

2. 重构选项打乱逻辑，仅在加载新题时执行
   创建一个专门加载并打乱当前题目选项的方法，替换原来的shuffleAnswers()：

func loadCurrentQuestionAnswers() {
    guard !api.QnAData.isEmpty, currentQuestionIndex < api.QnAData.count else {
        currentShuffledAnswers = []
        return
    }
    let currentQuestion = api.QnAData[currentQuestionIndex]
    var answers = currentQuestion.incorrectAnswers
    answers.append(currentQuestion.correctAnswer)
    // 解码并打乱选项，结果存入状态变量
    currentShuffledAnswers = answers.compactMap { $0.removingPercentEncoding }.shuffled()
}

3. 在合适时机触发选项加载

• 视图首次出现时加载初始题目选项：

.onAppear {
    loadCurrentQuestionAnswers()
}

• 点击「Next」按钮切换题目后，重新加载新题的打乱选项：

Button("Next") {
    currentQuestionIndex += 1
    // 重置答题状态
    answerSelected = nil
    hasUserAnswered = false
    // 加载新题的打乱选项
    loadCurrentQuestionAnswers()
}
.disabled(!hasUserAnswered) // 保持原有的未答题不可点击逻辑

4. 修改ForEach遍历状态变量
   把原来ForEach(shuffleAnswers(), id: \.self)改成遍历存储好的currentShuffledAnswers，避免每次重绘都重新打乱：

if !api.QnAData.isEmpty {
    ForEach(currentShuffledAnswers, id: \.self) { shuffledAnswer in
        Button(action: {
            guard answerSelected == nil else { return }
            
            let decodedAnswer = shuffledAnswer.removingPercentEncoding ?? shuffledAnswer
            answerSelected = decodedAnswer
            hasUserAnswered = true
            
            // 判断答案是否正确并更新得分
            let correctAnswer = api.QnAData[currentQuestionIndex].correctAnswer.removingPercentEncoding ?? api.QnAData[currentQuestionIndex].correctAnswer
            if decodedAnswer == correctAnswer {
                score += 1
                print("答对了，当前得分：\(score)")
            } else {
                print("答错了，当前得分：\(score)")
            }
        }) {
            Text(shuffledAnswer)
            // 保留你原有的按钮样式代码
        }
    }
}

为什么原来的写法会出问题？ #

SwiftUI是状态驱动的视图框架，当answerSelected、hasUserAnswered这类状态变量变化时，整个View会重新渲染。原来在ForEach里直接调用shuffleAnswers()，相当于每次渲染都执行一次打乱逻辑，所以用户选完答案后状态变化触发重绘，选项就被重新打乱了。

内容的提问来源于stack exchange，提问作者AranAli