iosswiftnskeyedunarchiverios12

Unarchive Array with NSKeyedUnarchiver unarchivedObject(ofClass:from:)


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?


Solution

  • 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:


    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.