将数据保存到pList：`无法将类型'__NSCFDictionary'的值转换为'NSMutableArray'错误

Question

我收到以下错误：

Could not cast value of type '__NSCFDictionary' (0x10dccdef0) to 'NSMutableArray' (0x10dccd978)

我正在使用本教程：http://sweettutos.com/2015/06/03/swift-how-to-read-and-write-into-plist-files/ 但是，当我使用保存功能时：

func saveScore() {

    // Save note to plist
    let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
    let pathForThePlistFile = appDelegate.plistPathInDocument

    // Extract the content of the file as NSData

    let data:NSData =  NSFileManager.defaultManager().contentsAtPath(pathForThePlistFile)!
    // Convert the NSData to mutable array

    do{
        let scoresArray = try NSPropertyListSerialization.propertyListWithData(data, options: NSPropertyListMutabilityOptions.MutableContainersAndLeaves, format: nil) as! NSMutableArray

        scoresArray.addObject(self.totalScoreLabel.text!)

        // Save to plist
        scoresArray.writeToFile(pathForThePlistFile, atomically: true)

    }catch{

        print("An error occurred while writing to plist")
    }

scoreArray是： var scoresArray:NSMutableArray!

对于pList路径，我按照教程中的指示在AppDelegate中使用此代码，从而创建“scores.plist”文件。

var plistPathInDocument:String = String()

func preparePlistForUse(){

    // 1
    let rootPath = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, .UserDomainMask, true)[0]

    // 2
    plistPathInDocument = rootPath.stringByAppendingString("/scores.plist")
    if !NSFileManager.defaultManager().fileExistsAtPath(plistPathInDocument){
        let plistPathInBundle = NSBundle.mainBundle().pathForResource("scores", ofType: "plist") as String!

    // 3
do {
    try NSFileManager.defaultManager().copyItemAtPath(plistPathInBundle, toPath: plistPathInDocument)
    }catch{
            print("Error occurred while copying file to document \(error)")
        }
    }
}

我确保得分.plist文件的根目录是“数组”，而不是字典。

我在这里看到了同样的问题：Swift. SIGABRT: cast value of type '__NSCFDictionary' to 'NSMutableArray'但是没有答案，请帮忙。

以下是我的pList的外观：