ios - 从数组中选择随机结构

Question

在用户开始测验之前，我有一个随机化的结构数组。我想从这个数组中随机得到 3 个问题并将它们放入一个新数组中。最好的方法是什么？

我应该在选择随机结构之前打乱数组还是有办法选择随机结构？

到目前为止，我能弄清楚如何执行此操作的唯一方法是预先打乱数组，然后附加前 3 个响应。

var learnersQuizQuestions =

[
    questionInfo(question: "Question 0", questionNumber: 1, answer: true, explanation: "Explanation for Question 0"),
    questionInfo(question: "Question 1", questionNumber: 2, answer: true, explanation: "Explanation for Question 1"),
    questionInfo(question: "Question 2", questionNumber: 3, answer: true, explanation: "Explanation for Question 2"),
    questionInfo(question: "Question 3", questionNumber: 4, answer: true, explanation: "Explanation for Question 3"),
    questionInfo(question: "Question 4", questionNumber: 5, answer: true, explanation: "Explanation for Question 4")
                                                                        ]

Answer 1

只需混合数组并选择前三个元素。

for var i:Int = 0; i < 10; ++i{
    randIdx1 = Int(arc4random() % learnersQuizQuestions.count)
    randIdx2 = Int(arc4random() % learnersQuizQuestions.count)
    swap(&learnersQuizQuestions[randIdx1], &learnersQuizQuestions[randIdx1])
}

let firstQuestion = learnersQuizQuestions[0]
let secondQuestion = learnersQuizQuestions[1]
let thirdQuestion = learnersQuizQuestions[2]