将更改后的数组重置为其原始值 Swift

Question

我有一个数组。我需要使用随机数生成器循环遍历所有数组元素并且不希望重复。

编码新手，我在使用后将数组元素值设置为“”即兴创作。

再次选择数组元素时，我检查新数组的数组元素值是否与原来的相等。如果不是，我输入一个新的随机索引号并重试。

---

这适用于下面显示的两种方式，直到 restart (startover())

然而

''' 当我设置 remainingQuestions = allQuestions -重启后它不起作用。结果 = 每次重启时文本的（“”/空白）值数量增加。

''' 当我设置 remainingQuestions = questionBank() -它总是有效

但是为什么 >.

澄清：我不明白上述两者之间的区别。两者都应该指向同一个数组？为什么一种有效，一种无效。我所做的只是将剩余问题指向一个包含相同数组的变量。

我的代码无效代码 //注释掉：

//Model: File - Question ------------------------------------------

    class Question {

        var questionText : String
        let answer : Bool

        init(text: String, correctAnswer: Bool) {
            questionText = text
            answer = correctAnswer
        }
    }

//Model: File - QuestionBank --------------------------------------

    class QuestionBank {
        var list = [question]()

        init() {

            list.append(Question(text: "", correctAnswer: ""))
        }
    }

//Controller: File - ViewController -------------------------------

    var remainingQuestions = QuestionBank()                             
    //var allQuestions = QuestionBank()
    var questionNumber = Int.random(in: 0..<13)
    var count : Int = 0

    //Iteration snippet: ------------------------------------------

    @IBAction func answerPressed(_ sender: AnyObject) {

        count += 1

        remainingQuestions.list[questionNumber].questionText = ""

        questionNumber = Int.random(in: 0..<13)

        nextQuestion()


    }

        func nextQuestion() {
            if count < 13 {
                if remainingQuestions.list[questionNumber].questionText == questionBank().list[questionNumber].questionText {
                    //this works
                //if remainingQuestions.list[questionNumber].questionText == allQuestions.list[questionNumber].questionText {
                    //this works until startOver()

                    questionLabel.text = remainingQuestions.list[questionNumber].questionText

                } else {
                questionNumber = Int.random(in: 0..<13)
                nextQuestion()
                }

            } else {
                startOver()
        }

        func startOver() {
            count = 0
            score = 0
            remainingQuestions = QuestionBank() //This works
            // remainingQuestions = allQuestions (This doesn't work (why!?))
            nextQuestion()
    }

Answer 1

给你一个洗牌数组的实际例子......

在任何视图控制器的viewDidLoad() 中添加这个：

let questions:[String] = [
    "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten"
]
for _ in 1...4 {
    let shuffledQuestions:[String] = questions.shuffled()
    print(shuffledQuestions)
}

当您运行此程序时，您将在调试控制台中看到问题数组输出四次，每次以随机顺序输出。它看起来像这样：

["Six", "Nine", "One", "Five", "Four", "Two", "Ten", "Three", "Eight", "Seven"]
["Two", "Nine", "Seven", "Four", "Six", "Five", "Eight", "One", "Three", "Ten"]
["Nine", "Ten", "Four", "Two", "One", "Five", "Eight", "Three", "Six", "Seven"]
["Six", "Three", "Seven", "One", "Five", "Two", "Eight", "Nine", "Four", "Ten"]

当然，每次运行，顺序都会不同。

所以，这里有一个简单的 10 题真/假测验的完整示例，问题顺序是随机的（打乱的）。回答完第 10 个问题后，您可以点击“重新开始测验”按钮，您将得到相同的 10 个问题，但顺序不同：

//Model: File - Question ------------------------------------------

class Question {

    var questionText : String
    let answer : Bool

    init(text: String, correctAnswer: Bool) {
        questionText = text
        answer = correctAnswer
    }
}

//Model: File - QuestionBank --------------------------------------

class QuestionBank {
    var list: [Question] = [
        Question(text: "One is an Even number?",   correctAnswer: false),
        Question(text: "Two is an Even number?",   correctAnswer: true),
        Question(text: "Three is an Even number?", correctAnswer: false),
        Question(text: "Four is an Even number?",  correctAnswer: true),
        Question(text: "Five is an Even number?",  correctAnswer: false),
        Question(text: "Six is an Even number?",   correctAnswer: true),
        Question(text: "Seven is an Even number?", correctAnswer: false),
        Question(text: "Eight is an Even number?", correctAnswer: true),
        Question(text: "Nine is an Even number?",  correctAnswer: false),
        Question(text: "Ten is an Even number?",   correctAnswer: true),
    ]
}

class RandomizeQuestionsViewController: UIViewController {

    let questionHeaderLabel: UILabel = {
        let v = UILabel()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = .cyan
        v.numberOfLines = 0
        v.textAlignment = .center
        return v
    }()

    let questionLabel: UILabel = {
        let v = UILabel()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = .yellow
        v.numberOfLines = 0
        v.textAlignment = .center
        return v
    }()

    let answerLabel: UILabel = {
        let v = UILabel()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = .yellow
        v.numberOfLines = 0
        v.textAlignment = .center
        return v
    }()

    let nextButton: UIButton = {
        let v = UIButton()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = .blue
        v.setTitle("Next Question", for: .normal)
        return v
    }()

    let restartButton: UIButton = {
        let v = UIButton()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = .red
        v.setTitle("Restart Quiz", for: .normal)
        return v
    }()

    let trueButton: UIButton = {
        let v = UIButton()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = UIColor(white: 0.9, alpha: 1.0)
        v.setTitleColor(.lightGray, for: .disabled)
        v.setTitleColor(.blue, for: .normal)
        v.layer.borderColor = UIColor.red.cgColor
        v.setTitle("True", for: .normal)
        return v
    }()

    let falseButton: UIButton = {
        let v = UIButton()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = UIColor(white: 0.9, alpha: 1.0)
        v.setTitleColor(.blue, for: .normal)
        v.setTitleColor(.lightGray, for: .disabled)
        v.layer.borderColor = UIColor.red.cgColor
        v.setTitle("False", for: .normal)
        return v
    }()


    var shuffledQuestions: [Question] = [Question]()

    // arrays are zero-based
    var currentQuestionIndex: Int = 0

    override func viewDidLoad() {
        super.viewDidLoad()

        // add UI elements
        view.addSubview(questionHeaderLabel)
        view.addSubview(questionLabel)
        view.addSubview(trueButton)
        view.addSubview(falseButton)
        view.addSubview(answerLabel)
        view.addSubview(nextButton)
        view.addSubview(restartButton)

        NSLayoutConstraint.activate([

            questionHeaderLabel.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 40.0),
            questionHeaderLabel.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor, constant: 40.0),
            questionHeaderLabel.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor, constant: -40.0),
            questionHeaderLabel.heightAnchor.constraint(equalToConstant: 30.0),

            questionLabel.topAnchor.constraint(equalTo: questionHeaderLabel.bottomAnchor, constant: 0.0),
            questionLabel.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor, constant: 40.0),
            questionLabel.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor, constant: -40.0),
            questionLabel.heightAnchor.constraint(equalToConstant: 80.0),

            trueButton.topAnchor.constraint(equalTo: questionLabel.bottomAnchor, constant: 40.0),
            trueButton.centerXAnchor.constraint(equalTo: view.centerXAnchor, constant: -60.0),
            trueButton.widthAnchor.constraint(equalToConstant: 90.0),

            falseButton.topAnchor.constraint(equalTo: questionLabel.bottomAnchor, constant: 40.0),
            falseButton.centerXAnchor.constraint(equalTo: view.centerXAnchor, constant: 60.0),
            falseButton.widthAnchor.constraint(equalToConstant: 90.0),

            answerLabel.topAnchor.constraint(equalTo: trueButton.bottomAnchor, constant: 40.0),
            answerLabel.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor, constant: 40.0),
            answerLabel.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor, constant: -40.0),
            answerLabel.heightAnchor.constraint(equalToConstant: 80.0),

            nextButton.topAnchor.constraint(equalTo: answerLabel.bottomAnchor, constant: 40.0),
            nextButton.centerXAnchor.constraint(equalTo: view.centerXAnchor, constant: 0.0),
            nextButton.widthAnchor.constraint(equalToConstant: 160.0),

            restartButton.topAnchor.constraint(equalTo: answerLabel.bottomAnchor, constant: 40.0),
            restartButton.centerXAnchor.constraint(equalTo: view.centerXAnchor, constant: 0.0),
            restartButton.widthAnchor.constraint(equalToConstant: 160.0),

            ])

        trueButton.addTarget(self, action: #selector(trueTapped(_:)), for: .touchUpInside)
        falseButton.addTarget(self, action: #selector(falseTapped(_:)), for: .touchUpInside)
        nextButton.addTarget(self, action: #selector(nextQuestionTapped(_:)), for: .touchUpInside)
        restartButton.addTarget(self, action: #selector(restartQuizTapped(_:)), for: .touchUpInside)

        restartQuizTapped(nil)

    }

    @objc func restartQuizTapped(_ sender: Any?) -> Void {

        // hide restart button
        restartButton.isHidden = true

        // nextQuestion func increments the index...
        // set it to -1 so the first question will be index 0
        currentQuestionIndex = -1

        // shuffle the questions
        shuffledQuestions = QuestionBank().list.shuffled()

        // show the question
        nextQuestionTapped(nil)

    }

    @objc func nextQuestionTapped(_ sender: Any?) -> Void {

        // hide next button
        nextButton.isHidden = true

        // reset true/false button borders
        trueButton.layer.borderWidth = 0
        falseButton.layer.borderWidth = 0

        // increment the index
        currentQuestionIndex += 1

        if currentQuestionIndex < shuffledQuestions.count {

            // get current Question object from shuffled array
            let q: Question = shuffledQuestions[currentQuestionIndex]

            // set the label texts
            questionHeaderLabel.text = "Question \(currentQuestionIndex + 1) of \(shuffledQuestions.count)"
            questionLabel.text = q.questionText
            answerLabel.text = "Select True or False"

            // enable true/false buttons
            trueButton.isEnabled = true
            falseButton.isEnabled = true

        } else {

            // out of questions, so show restart button
            restartButton.isHidden = false

        }

    }

    @objc func trueTapped(_ sender: Any?) -> Void {

        // highlight selected button
        trueButton.layer.borderWidth = 3

        // get current Question object from shuffled array
        let q: Question = shuffledQuestions[currentQuestionIndex]

        var answerText = ""

        if q.answer == true {
            answerText = "Correct!" + "\n" + "It IS an Even number!"
        } else {
            answerText = "Wrong!" + "\n" + "It is NOT an Even number!"
        }

        updateUI(feedback: answerText)

    }

    @objc func falseTapped(_ sender: Any?) -> Void {

        // highlight selected button
        falseButton.layer.borderWidth = 3

        // get current Question object from shuffled array
        let q: Question = shuffledQuestions[currentQuestionIndex]

        var answerText = ""

        if q.answer == false {
            answerText = "Correct!" + "\n" + "It is NOT an Even number!"
        } else {
            answerText = "Wrong!" + "\n" + "It IS an Even number!"
        }

        updateUI(feedback: answerText)

    }

    func updateUI(feedback answer: String) -> Void {

        answerLabel.text = answer

        // disable true/false buttons
        trueButton.isEnabled = false
        falseButton.isEnabled = false

        // if there are more questions
        if currentQuestionIndex < shuffledQuestions.count - 1 {
            // show next question button
            nextButton.isHidden = false
        } else {
            // show restart button
            restartButton.isHidden = false
        }

    }

}

这都是基于代码的，所以没有@IBOutlets 或@IBActions ...只需从一个新的视图控制器开始，并将其类分配给RandomizeQuestionsViewController。

Answer 2

我会做一些不同的事情。您的示例中缺少很多代码，因此需要进行一些更改，但要点如下：

import UIKit

class Question {

  let questionText : String
  let answer : Bool

  init(text: String, correctAnswer: Bool) {
    questionText = text
    answer = correctAnswer
  }
}

//Model: File - QuestionBank --------------------------------------

class QuestionBank {
  var list = [Question]()

  init() {
    list.append(Question(text: "", correctAnswer: false))
  }

  init(list: [Question]) {
    self.list = list
  }

  func pop() -> Question? {
    guard list.count > 0 else {
      return nil
    }
    return list.removeFirst()
  }
}



//Controller: File - ViewController -------------------------------

var remainingQuestions = QuestionBank()
var allQuestions = QuestionBank()

//Iteration snippet: ------------------------------------------

func answerPressed() {
  nextQuestion()
}

func nextQuestion() {
  guard let nextQuestion = remainingQuestions.pop() else {
      print("no questions left")
      startOver()
      return
  }
      questionLabel.text = nextQuestion.questionText
  }

  func startOver() {//also call on first setup
    remainingQuestions = QuestionBank(list: allQuestions.list.shuffled())

    nextQuestion()
  }