ios - 使用 NSUserDefaults 保存标签的文本

Question

我正在尝试使用 NSUserDefaults 保存我的分数。我希望它保存标签文本，因此当您重新打开它时，文本仍然存在。我不知道代码应该去哪里。非常感谢任何帮助。

这是我的代码:

import UIKit
import AVFoundation

struct Question {
    var Question : String!
    var Answers : [String]!
    var Answer : Int!
}

class ViewController: UIViewController {
    @IBOutlet weak var highScoreLbl: UILabel!
    @IBOutlet var Buttons: [UIButton]!
    @IBOutlet weak var QLabel: UILabel!
    @IBOutlet weak var Label: UILabel!
    @IBOutlet weak var incorrectLabel: UILabel!
    @IBOutlet weak var timerLabel: UILabel!
    @IBOutlet weak var theEnd: UILabel!
    @IBOutlet weak var continueButton: UIButton!
    @IBOutlet weak var button1: UIButton!
    @IBOutlet weak var button2: UIButton!
    @IBOutlet weak var button3: UIButton!
    @IBOutlet weak var button4: UIButton!

    var scoreLbl = UILabel()
    var score = Int()
    var Questions = [Question]()
    var QNumber = Int()
    var AnswerNumber = Int()
    var wrongAnswers = Int()
    var highScore = 0

    override func viewDidLoad() {
        super.viewDidLoad()

        Questions = [Question(Question: "What is the Biggest Hit of Bing Crosby?" , Answers: ["Swinging on a Star", "Now is the Hour", "White Christmas", "Beautiful Dreamer"], Answer: 2),
        Question(Question: "What is Elvis Presely's Middle Name?", Answers: ["Aaron", "Micheal", "George", "Matthew"], Answer: 0),
        Question(Question: "How Many Oscars did Titanic win?", Answers: ["5", "7", "10", "11"], Answer: 3),
        Question(Question: "From which country did Pitta Bread originate?", Answers: ["Spain", "France", "Greece", "Russia"], Answer: 2),
        Question(Question: "What is the largest living creature on Earth?", Answers: ["Whale", "Shark", "Sea Turtle", "Alligator"], Answer: 0),
        Question(Question: "What does ATM stand for?", Answers: ["Automatic Treasure Machine", "Automatic Tax Machine", "Anti Tax Machine", "Automatic Teller Machine"], Answer: 3),
        Question(Question: "What's the world's second largest French speaking city?", Answers: ["Paris", "Montreal", "Versailles", "Québec"], Answer: 1),
        Question(Question: "What Country is the largest producer of Olive Oil?", Answers: ["Italy", "France", "Greece", "Spain"], Answer: 3),
        Question(Question: "How long is the Great Wall of China?", Answers: ["3200 miles", "4000 miles", "2000 kilometers", "4500 miles"], Answer: 1),
        Question(Question: "Who is on the 10 dollar bill?", Answers: ["George Washington", "Thomas Jefferson", "Alexander Hamilton", "John Adams" ], Answer: 2),
        Question(Question: "How many World Series did Yogi Berra win as a player?", Answers: ["11", "10", "5", "7" ], Answer: 1),
        Question(Question: "Which three countries hosted the Winter Olympics during the 1990's?", Answers: ["Norway, France, Russia", "US, Sweeden, Canada", "Japan, Canada, Germany", "Slovenia, France, South Korea" ], Answer: 0),]

        scoreLbl = UILabel(frame: CGRectMake(35, 45, 77, 45))
        scoreLbl.textAlignment = NSTextAlignment.Center
        scoreLbl.text = "-1"
        self.view.addSubview(scoreLbl)

        PickQuestions()

        saveHighScore()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func PickQuestions(){

        score++
        scoreLbl.text = "\(score)"

        if Questions.count > 0{
            QNumber = random() % Questions.count
            QLabel.text = Questions[QNumber].Question

            AnswerNumber = Questions[QNumber].Answer

            for i in 0..<Buttons.count{
                Buttons[i].setTitle(Questions[QNumber].Answers[i], forState: UIControlState.Normal)
            }

            Questions.removeAtIndex(QNumber)
        }
        else{

            theEnd.text = "You Win!"
            theEnd.alpha = 1
            button1.enabled = false
            button2.enabled = false
            button3.enabled = false
            button4.enabled = false

            func reset(){
                let alert = UIAlertController(title: "You Win", message: "Click Restart To Play Again", preferredStyle: UIAlertControllerStyle.Alert)
                let okAction = UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil)
                alert.addAction(okAction)
                presentViewController(alert, animated: true, completion: nil)
            }
            reset()
        }

        saveHighScore()
        incorrectLabel.alpha = 0

    }

    func saveHighScore(){

        if score >= highScore {
            highScore = score
            highScoreLbl.text = "High Score: " + String(score)

        }
        else{}

    }
    @IBAction func Btn1(sender: AnyObject) {
        if AnswerNumber == 0{
            PickQuestions()
        }
        else{
            incorrectLabel.text = "You are incorrect!"
            incorrectLabel.alpha = 1
            score--
            scoreLbl.text = "\(score)"
        }

    }
    @IBAction func Btn2(sender: AnyObject) {
        if AnswerNumber == 1{

            PickQuestions()
        }
        else{
            incorrectLabel.text = "You are Incorrect!"
            incorrectLabel.alpha = 1
            score--
            scoreLbl.text = "\(score)"
        }
    }
    @IBAction func Btn3(sender: AnyObject) {
        if AnswerNumber == 2{

            PickQuestions()
        }
        else{
            incorrectLabel.text = "You are Incorrect!"
            incorrectLabel.alpha = 1
            score--
            scoreLbl.text = "\(score)"
        }
    }
    @IBAction func Btn4(sender: AnyObject) {
        if AnswerNumber == 3{

            PickQuestions()
        }
        else{
            incorrectLabel.text = "You are Incorrect!"
            incorrectLabel.alpha = 1
            score--
            scoreLbl.text = "\(score)"
        }
    }
}

Answer 1

您可以使用属性观察者来做到这一点。每次您设置分数时，您的 didSet block 都会检查您的分数是否大于之前的高分，如果是，它将运行并将您的高分存储到您的 NSUserDefaults 中。

"Property observers observe and respond to changes in a property’s value. Property observers are called every time a property’s value is set, even if the new value is the same as the property’s current value."

有关属性(property)观察员的更多信息:Swift Programming Language Guide

var userDefaults = NSUserDefaults.standardUserDefaults()

var score: Int = 0 {
        didSet {
            self.scoreLbl.text = "\(score)"

            if score > highScore {
                // you could just as easily call a function here
                userDefaults.setInteger(score, forKey: "CurrentHighScore")
                //userDefaults.synchronize() // slow and unnecessary!
            } 
        }
    }

然后在你的 viewDidLoad 或 viewWillAppear 中检索你的高分值:

override func viewDidLoad() {

    self.scoreLbl.text = userDefaults.integerForKey("CurrentHighScore")

}

iOS 8 及更高版本不需要同步:

来自http://www.codingexplorer.com/nsuserdefaults-a-swift-introduction/

Calling synchronize in an iOS 8 app will unnecessarily slow your program, without giving a significant benefit. I’ll let the document speak for itself about the Performance Tradeoffs in NSUserDefaults:

"Reading from NSUserDefaults is extremely fast. It will cache values to avoid reading from the disk, and takes about 0.5 microseconds to do [[NSUserDefaults standardUserDefaults] boolForKey:] on a 2012 MacBook Pro. It’s generally unnecessary (and even undesirable since it prevents picking up new values) to cache the result of reading from preferences.

However, writing to NSUserDefaults is a bit slower. In general, expect it to take roughly as long as using NSPropertyListSerialization to convert your key and value to plist data, plus a few 10s of microseconds. For this reason, as well as memory usage, it’s generally best to store relatively small data in CFPreferences."