Saving a SpriteKit game in Swift 3

Swift3Save.swift

import SpriteKit

class GameData : NSObject, NSCoding {
    
    /// Current game slot being played "One" to "Four"
    var currentSaveFile : String? = nil
    
    /// A string to save
    var variableA : String = "AString"
    
    /// Reference to LevelData array which contains both static and saved data
    var levelData : LevelData?
    
    /// Money in the bank
    var bank : Int = 200
    
    /// Units available to recruit
    var food : Int = 0
    
    /// Create of shared instance
    internal static let sharedInstance = GameData()
    
    // MARK: Init
    
    override init() {
        super.init()
        
        /// Create default data for vairables that havent been set
        self.levelData = LevelData()
    }
    
    required init?(coder: NSCoder) {
        super.init()
        self.variableA = coder.decodeObject(forKey: "variableA") as! String
        self.bank = coder.decodeInteger(forKey: "bank")
        self.food = coder.decodeInteger(forKey: "food")
        self.levelData = coder.decodeObject(forKey: "levelData") as? LevelData
    }
    
    func encode(with coder: NSCoder) {
        coder.encode(GameData.sharedInstance.variableA, forKey: "variableA")
        coder.encode(GameData.sharedInstance.bank, forKey: "bank")
        coder.encode(GameData.sharedInstance.food, forKey: "food")
        coder.encode(GameData.sharedInstance.levelData, forKey: "levelData")
    }
    
    func resetData() {
        self.bank = 200
        self.food = 0
        self.variableA = "AString"
        self.levelData = LevelData()
        
        /// Even though same static instance of GameData, this flag controls which save file we're dealing with
        self.currentSaveFile = nil
    }
    
    // MARK: Loading and saving
    
    /// This loads an existing game, or starts a new slot for a new game.
    func loadGame(saveFile:String) -> Bool {
        
        /// Make sure we're not holding on to past game data
        self.resetData()
        
        /// Specifcy save file to work with
        self.currentSaveFile = saveFile
        
        /// If save file exists already, load it in and assign variables
        if let savedData = self.loadGameData(file:saveFile) {
            self.levelData = savedData.levelData
            self.food = savedData.food
            self.bank = savedData.bank
            self.variableA = savedData.variableA
            
            return true
        }
        return false
    }
    
    /// Internal method to actual load the file
    private func loadGameData(file:String) -> GameData? {
        
        /// load existing high scores or set up an empty array
        let path = GameData.getFilePath(name:file)
        
        /// Only attempt to decode if file already existed
        if GameData.fileExistsAtPath(path:path, create: true) {
            
            if let rawData = NSData(contentsOfFile: path) {
                /// do we get serialized data back from the attempted path?
                /// if so, unarchive it into an AnyObject, and then convert to a GameData object
                if let data = NSKeyedUnarchiver.unarchiveObject(with: rawData as Data) as? GameData {
                    return data
                }
            }
            
        }
        
        return nil
    }
    
    func save() {
        
        /// If we're working with an active save file, attempt to save it
        if let saveFile = self.currentSaveFile {
            
            DispatchQueue.global(attributes: .qosBackground).async {
                
                /// find the save directory our app has permission to use, and save the serialized version of self.scores - the HighScores array.
                let saveData = NSKeyedArchiver.archivedData(withRootObject: GameData.sharedInstance)
                let path = GameData.getFilePath(name: saveFile)
                
                do {
                    let location = URL(fileURLWithPath: path)
                    try saveData.write(to:location, options: .atomicWrite)
                } catch _ {
                    print("unable to save file")
                }
            }
            
        }
        
    }
    
    // MARK: Files
    
    /// This would create a file in the documents directory of GameDataOne.plist
    class func getFilePath(name:String) -> String {
        let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
        let documentsDirectory = paths[0] as String
        let fileName = "/GameData\(name)"
        let path = documentsDirectory + "\(fileName).plist"
        return path
    }
    
    /// Check if a file exists. Pass in create = true to create the file if it doesn't exist.
    /// Requires DefaultFile.plist to be an empty plist in your project directory
    class func fileExistsAtPath(path:String, create:Bool = false) -> Bool {
        let fileManager = FileManager.default()
        if !fileManager.fileExists(atPath: path) {
            // create an empty file if it doesn't exist and create is true
            if(create) {
                if let bundle = Bundle.main().pathForResource("DefaultFile", ofType: "plist") {
                    do {
                        try fileManager.copyItem(atPath: bundle, toPath: path)
                    } catch _ {
                        print("Unable to create base save file")
                    }
                }
                else {
                    print("DefaultFile not found")
                }
            }
            return false
        }
        return true
    }
    
    /// Delete a save file. Requires you to path in proper path by calling getFilePath first
    class func deleteFileAtPath(path:String) {
        let fileManager = FileManager.default()
        do {
            try fileManager.removeItem(atPath: path)
        } catch _ {
        }
    }
    
}

See this gist for Level data: https://gist.github.com/veeneck/96306731570687e76d1190fa6ccacf0c

Code using the class: https://gist.github.com/veeneck/1d988af6e20e67b131c9cf775f546f16

I'm getting an error at line 107 with DispatchQueue.global(attributes: .qosBackground).async. The error is that

Argument labels '(attributes:)' do not match any available overloads

Am I doing something wrong, or is there something slightly wrong with the code? Thanks for your help.

Use DispatchQueue.global(qos: .background).async { instead