ios - 如何在 Swift 中使用 NSCoding 存储从 ViewController 生成的值

Question

我有来自“ScoreHistory.swift”的以下变量:

// ScoreHistory.swift

class ScoreHistory: NSObject, NSCoding {

var datePlayed: NSDate
var totalScore: Int
var totalAnswered: Int
var totalDuration: Int
var gameStatus: String

在我的 QuizViewController 中，我有以下变量:

// QuizViewController.swift

var datePlayed = NSDate()
var totalScore = 0
var totalAnswered = 0
var totalDuration = 0
var gameStatus: String?

每次游戏结束后，用户可能会得到以下信息:(显示在“ScoreViewController”中)

// Example data

datePlayed: (date today)
totalScore: 10
totalAnswered: 15
totalDuration: 1 min. 3 sec.
gameStatus: Exam Finished

我需要从 QuizViewController 获取上述数据以存储到“ScoreHistory.swift”我需要在 ScoreViewController.swift 中显示数据:

// ScoreViewController.swift

class ScoreViewController: UIViewController, UINavigationControllerDelegate {

// in viewDidLoad()

if let score = score {

    navigationItem.title = score.datePlayed.description
    datePlayedLabel.text = score.datePlayed.description
    totalScoreLabel.text   = score.totalScore.description
    totalAnsweredLabel.text   = score.totalAnswered.description
    totalDurationLabel.text   = score.totalDuration.description
    gameStatusLabel.text   = score.gameStatus
}

如何将从 QuizViewContoller 生成的数据存储到 ScoreHistory？以及如何将上述数据显示到 ScoreViewController？

我的 ScoreHistory 看起来像这样:

class ScoreHistory: NSObject, NSCoding {

// MARK: Properties

var datePlayed: NSDate
var totalScore: Int
var totalAnswered: Int
var totalDuration: Int
var gameStatus: String

// MARK: Archiving Paths

static let DocumentsDirectory = NSFileManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).first!
static let ArchiveURL = DocumentsDirectory.URLByAppendingPathComponent("scores")

// MARK: Types

struct PropertyKey {
    static let datePlayedKey = "datePlayed"
    static let totalScoreKey = "totalScore"
    static let totalAnsweredKey = "totalAnswered"
    static let totalDurationKey = "totalDuration"
    static let gameStatusKey = "gameStatus"
}

// MARK: Initialization

init?(datePlayed: NSDate, totalScore: Int, totalAnswered: Int, totalDuration: Int, gameStatus: String) {
    // Initialize stored properties.

    self.datePlayed = datePlayed
    self.totalScore = totalScore
    self.totalAnswered = totalAnswered
    self.totalDuration = totalDuration
    self.gameStatus = gameStatus


    super.init()

    // Initialization should fail if there is no name or if the rating is negative.
    if gameStatus.isEmpty {
        return nil
    }
}

// MARK: NSCoding

func encodeWithCoder(aCoder: NSCoder) {

    aCoder.encodeObject(datePlayed, forKey: PropertyKey.datePlayedKey)
    aCoder.encodeInteger(totalScore, forKey: PropertyKey.totalScoreKey)
    aCoder.encodeInteger(totalAnswered, forKey: PropertyKey.totalAnsweredKey)
    aCoder.encodeInteger(totalDuration, forKey: PropertyKey.totalDurationKey)
    aCoder.encodeObject(gameStatus, forKey: PropertyKey.gameStatusKey)
}

required convenience init?(coder aDecoder: NSCoder) {

    let datePlayed = aDecoder.decodeObjectForKey(PropertyKey.datePlayedKey) as? NSDate
    let totalScore = aDecoder.decodeIntegerForKey(PropertyKey.totalScoreKey)
    let totalAnswered = aDecoder.decodeIntegerForKey(PropertyKey.totalAnsweredKey)
    let totalDuration = aDecoder.decodeIntegerForKey(PropertyKey.totalDurationKey)
    let gameStatus = aDecoder.decodeObjectForKey(PropertyKey.gameStatusKey) as! String

    // Must call designated initializer.
    self.init(datePlayed: datePlayed!, totalScore: totalScore, totalAnswered: totalAnswered, totalDuration: totalDuration, gameStatus: gameStatus)
}

}

Answer 1

我不确定我是否正确理解了您的问题。您的问题是:

1. 如何将您的分数历史记录存储到文件中。
2. 如何将更改的信息从一个 View Controller 获取到另一个 View Controller 。

根据您提供的代码我无法弄清楚。

回答1。您在 ScoreHistory 类中正确实现了 NSCoding 方法。我在这里假设这是您的模型类，它必须保存在整个游戏中收集的数据。要将数据保存到文件中，您只需使用 NSKeyedArchiver 对象即可。代码示例如下:

    func saveStatisticsToDisk() {
    let isSuccessfulSave = NSKeyedArchiver.archiveRootObject(savedScore, toFile: ScoreHistory.scoreStore.path!)

    if !isSuccessfulSave {
        //Set the alert properties.
        let title = "Warning"
        let message = "Unable to save the scores"
        let animationFlag = true

        //configure the alert.
        let alertMessage = UIAlertController.init(title: title, message: message, preferredStyle: .Alert)
        let okAction = UIAlertAction(title: "Ok", style: .Default) {
            (action) -> Void in
            self.presentingViewController?.dismissViewControllerAnimated(animationFlag, completion: nil)
        }
        alertMessage.addAction(okAction)

        //Present the alert.
        self.presentViewController(alertMessage, animated: animationFlag, completion: nil)
    }
}

回答2。这比较复杂，因为您想要将数据从一个 View Controller 获取到另一个 View Controller 。编码最佳实践告诉您应该使用 NSNotifications 将更改从一个 View Controller 发送到另一个 View Controller 。这对于防止强引用循环是必要的。

这意味着在 QuizViewController 中您有一个 ScoreHistory 类的实例。我们称之为“quizScoreHistory”。在测验期间，实例 quizScoreHistory 会更新，当玩家完成一个关卡时，或者如您所说:“完成 session 后”，ScoreViewController 需要知道“quizScoreHistory”的详细信息是什么，以便它可以显示信息给玩家。

我在这里向您展示如何使用标准 NSNotification 的字典 use​​rInfo 来完成此操作。在 QuizViewController 类中，您使用以下代码将通知放置在默认通知中心:

    func notifyOnTrackChanges() {
//This function makes a dictionary with the key value pairs that reflect your ScoreHistory class.
//The a notification is posted under the name "scoreDidChange" posting the dictionary as userInfo. 
//The ScoreOverviewController will pick this up and store the values in the score to be displayed.

    let userInfo : [String: String] = ["date played": dateformatter.stringFromDate((self.quizScoreHistory.datePlayed)!), "total score": String((self.quizScoreHistory.totalScore)!), "total answered": String((self.quizScoreHistory.totalAnswered)!), "total duration": String((self.quizScoreHistory.gameStatus)!), "game status": String((self.quizScoreHistory.gameStatus)!)]
    let trackDetailNotificationCenter = NSNotificationCenter.defaultCenter()
    trackDetailNotificationCenter.postNotificationName("scoreDidChange", object: self, userInfo: userInfo)
}

我将 userInfo 作为字符串放入字典中，因为您只想在 ScoreViewController 中显示它们并理解您提供的代码，您只需要以字符串形式获取分数历史记录即可将其显示在单元格中。

现在您想在 ScoreViewController 中接收通知。可以在 viewDidLoad、viewWillAppear 中实现以下代码，或者更好地将其编写为 ScoreHistory 实例中的 setter。

        //This is the observer created to get the changes back from the QuizViewController.
    let notificationCenter = NSNotificationCenter.defaultCenter()
    let operationsQueue = NSOperationQueue.mainQueue()
    self.scoreChangedObserver = notificationCenter.addObserverForName("scoreDidChange", object: nil, queue: operationsQueue, usingBlock: { (notification: NSNotification!) -> Void in

        let score.datePlayed = notification.userInfo!["date played"]!
        let score.totalScore = notification.userInfo!["total score"]!
        let score.totalAnswered = notification.userInfo!["total answered"]!
        let score.totalDuration = notification.userInfo!["total duration"]!
        let score.gameStatus = notification.userInfo!["gameStatus"]!

        self.displayScore()
    })

假设分数是该方法的属性，您的显示分数可能会像您在问题中提供的那样:

func displayScore() {
    if let score = score {

        navigationItem.title = score.datePlayed
        datePlayedLabel.text = score.datePlayed
        totalScoreLabel.text   = score.totalScore
        totalAnsweredLabel.text   = score.totalAnswered
        totalDurationLabel.text   = score.totalDuration
        gameStatusLabel.text   = score.gameStatus
    }
}

我希望这能在某种程度上有所帮助。