如何不重复 Switch 的情况？ (Swift)

Question

我在做问答游戏。我在每个"case"的开关中预订了所有的问题和答案。我希望以随机顺序选择案例，但在该人回答问题并按下按钮 "next" 后，功能 "randomQuestions" 再次起作用，但我不希望重复以前使用过相同的案例。

func randomQuestions ()
{
    var randomNumber = arc4random_uniform(3)
    while previousNumber == randomNumber
    {
        randomNumber = arc4random_uniform(3)
    }
    previousNumber = randomNumber

    switch(randomNumber)
    {
    case 0:
        textoHideUnhide()
        questionsLabel.text = "What color is the sun?"
        button1.setTitle("Yellow", forState: UIControlState.Normal)
        button2.setTitle("Black", forState: UIControlState.Normal)
        button3.setTitle("Blue", forState: UIControlState.Normal)
        button4.setTitle("White", forState: UIControlState.Normal)
        correctAnswer = "1"
        break
    case 1:
        textoHideUnhide()
        questionsLabel.text = "What color is the moon?"
        button1.setTitle("Red", forState: UIControlState.Normal)
        button2.setTitle("Blue", forState: UIControlState.Normal)
        button3.setTitle("White", forState: UIControlState.Normal)
        button4.setTitle("Orange", forState: UIControlState.Normal)
        correctAnswer = "3"
        break
    case 2:
        textoHideUnhide()
        questionsLabel.text = "What color is the grass?"
        button1.setTitle("White", forState: UIControlState.Normal)
        button2.setTitle("Green", forState: UIControlState.Normal)
        button3.setTitle("Orange", forState: UIControlState.Normal)
        button4.setTitle("Red", forState: UIControlState.Normal)
        correctAnswer = "2"
        break
    default:
        break
}

Answer 1

您必须将变量 previousNumber 作为全局（实例）变量放在方法之外

var previousNumber = UInt32.max // declare the variable with an "impossible" value

func randomQuestions()
{
  var randomNumber : UInt32
  do {
    randomNumber = arc4random_uniform(3)
  } while previousNumber == randomNumber

  previousNumber = randomNumber

  switch(randomNumber) {
    ...

Answer 2

一种避免多次出现相同随机数的方法，您可以创建一个包含问题编号的数组，然后将其随机排列。

var indices = [0, 1, 2]

for i in 0 ..< indices.count {
    var temp = indices[i]
    var j = arc4random_uniform(indices.count)
    indices[i] = indices[j]
    indices[j] = temp
}

第一个问题是 indices[0] 提供的问题，当用户点击下一步时，你在 indices[1] 提出问题，依此类推。