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Since upgrading to Swift 4.2 I've found that many of the NSKeyedUnarchiver and NSKeyedArchiver methods have been deprecated and we must now use the type method static func unarchivedObject<DecodedObjectType>(ofClass: DecodedObjectType.Type, from: Data) -> DecodedObjectType? to unarchive data.

I have managed to successfully archive an Array of my bespoke class WidgetData, which is an NSObject subclass:

private static func archiveWidgetDataArray(widgetDataArray : [WidgetData]) -> NSData 

 guard let data = try? NSKeyedArchiver.archivedData(withRootObject: widgetDataArray as Array, requiringSecureCoding: false) as NSData
 else fatalError("Can't encode data") 

 return data

The problem comes when I try to unarchive this data:

static func loadWidgetDataArray() -> [WidgetData]? 

 if isKeyPresentInUserDefaults(key: USER_DEFAULTS_KEY_WIDGET_DATA) 

 if let unarchivedObject = UserDefaults.standard.object(forKey: USER_DEFAULTS_KEY_WIDGET_DATA) as? Data 

 //THIS FUNCTION HAS NOW BEEN DEPRECATED:
 //return NSKeyedUnarchiver.unarchiveObject(with: unarchivedObject as Data) as? [WidgetData]

 guard let nsArray = try? NSKeyedUnarchiver.unarchivedObject(ofClass: NSArray.self, from: unarchivedObject as Data) else 
 fatalError("loadWidgetDataArray - Can't encode data")
 

 guard let array = nsArray as? Array<WidgetData> else 
 fatalError("loadWidgetDataArray - Can't get Array")
 

 return array

 

 

 return nil

But this fails, as using Array.self instead of NSArray.self is disallowed. What am I doing wrong and how can I fix this to unarchive my Array?

You can use unarchiveTopLevelObjectWithData(_:) to unarchive the data archived by archivedData(withRootObject:requiringSecureCoding:). (I believe this is not deprecated yet.)

But before showing some code, you should better:

• Avoid using NSData, use Data instead




• Avoid using try? which disposes error info useful for debugging




• Remove all unneeded casts

Try this:

private static func archiveWidgetDataArray(widgetDataArray : [WidgetData]) -> Data 
 do 
 let data = try NSKeyedArchiver.archivedData(withRootObject: widgetDataArray, requiringSecureCoding: false)

 return data
 catch 
 fatalError("Can't encode data: (error)")
 



static func loadWidgetDataArray() -> [WidgetData]? 
 guard
 isKeyPresentInUserDefaults(key: USER_DEFAULTS_KEY_WIDGET_DATA), //<- Do you really need this line?
 let unarchivedObject = UserDefaults.standard.data(forKey: USER_DEFAULTS_KEY_WIDGET_DATA)
 else 
 return nil
 
 do 
 guard let array = try NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(unarchivedObject) as? [WidgetData] else 
 fatalError("loadWidgetDataArray - Can't get Array")
 
 return array
 catch 
 fatalError("loadWidgetDataArray - Can't encode data: (error)")
 

But if you are making a new app, you should better consider using Codable.

unarchiveTopLevelObjectWithData(_:) 

is deprecated as well. So to unarchive data without secure coding you need to:

1. Create NSKeyedUnarchiver with init(forReadingFrom: Data)
   


2. Set requiresSecureCoding of created unarchiver to false.


3. Call decodeObject(of: [AnyClass]?, forKey: String) -> Any? to get your object, just use proper class and NSKeyedArchiveRootObjectKeyas key.

 if #available(iOS 12.0, *) 
 guard let unarchivedFavorites = try? NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(favoritesData!)
 else 
 return
 
 self.channelFavorites = unarchivedFavorites as! [ChannelFavorite]
 else {
 if let unarchivedFavorites = NSKeyedUnarchiver.unarchiveObject(with: favoritesData!) as? [ChannelFavorite] 
 self.channelFavorites = unarchivedFavorites
 

// Achieving data

 if #available(iOS 12.0, *) 
 // use iOS 12-only feature
 do 
 let data = try NSKeyedArchiver.archivedData(withRootObject: channelFavorites, requiringSecureCoding: false)
 UserDefaults.standard.set(data, forKey: "channelFavorites")
 catch 
 return
 
 else 
 // handle older versions
 let data = NSKeyedArchiver.archivedData(withRootObject: channelFavorites)
 UserDefaults.standard.set(data, forKey: "channelFavorites")
 

This is the way I have updated my code and its working for me

You are likely looking for this:

if let widgetsData = UserDefaults.standard.data(forKey: USER_DEFAULTS_KEY_WIDGET_DATA) 
 if let widgets = (try? NSKeyedUnarchiver.unarchivedObject(ofClasses: [NSArray.self, WidgetData.self], from: widgetsData)) as? [WidgetData] 
 // your code