Problem updating to Swift 4.2

In iOS 11, some new methods were added to `NSKeyedUnarchiver` and `NSKeyedArchiver`, which throws Error instead of raising Exception on invalid input.

Direct alternative to this line:

return NSKeyedUnarchiver.unarchiveObject(with: tokenData) as? [String : CKServerChangeToken]

would be this:

return try? NSKeyedUnarchiver.unarchivedObject(ofClass: NSDictionary.self, from: tokenData) as? [String : CKServerChangeToken]

If you do not want to ignore errors silently, the code above would be:

do {
    return try NSKeyedUnarchiver.unarchivedObject(ofClass: NSDictionary.self, from: tokenData) as? [String : CKServerChangeToken]
} catch {
    print(error)
    return nil
}

And for your `set` code,

Direct alternative to this line:

let data = NSKeyedArchiver.archivedData(withRootObject: newValue)

Would be something like this:

guard let data = try? NSKeyedArchiver.archivedData(withRootObject: newValue, requiringSecureCoding: true) else {
    fatalError("archivedData failed")
}

Or:

do {
    let data = try NSKeyedArchiver.archivedData(withRootObject: newValue, requiringSecureCoding: true)
    //... use data inside this code block
} catch {
    fatalError("archivedData failed with error: \(error)")
}

In Swift Dictionary is a Generic Structure, and the previous method is waiting for a class.

Pass `NSDictionary.self`.

`NSKeyedArchiver` and `NSKeyedUnarchiver` uses `NSDictionary` for Swift `Dictionary` while archiving/unarchiving.

Thank you very much, I really apreciate your detailed answer, have a nice day!

Hi OOPer, I followed your approach, but now I am getting this error in the get{ } of dictionaryFetchChangeToken :

     do {
                return try NSKeyedUnarchiver.unarchivedObject(ofClass: NSDictionary.self, from: tokenData) as? [String : CKServerChangeToken]
            } catch {
                print(error)
                /*
                 Error Domain=NSCocoaErrorDomain Code=4864 "value for key 'NS.objects' was of unexpected class 'CKServerChangeToken'. Allowed classes are '{(
                 NSDictionary
                 )}'." UserInfo={NSDebugDescription=value for key 'NS.objects' was of unexpected class 'CKServerChangeToken'. Allowed classes are '{(
                 NSDictionary
                 )}'.}
                */
                return nil
            }

In the set { } prior to:

     guard let data = try? NSKeyedArchiver.archivedData(withRootObject: newValue, requiringSecureCoding: true) else {
                fatalError("archivedData failed")
            }

I print in the console newValue, and get:

po newValue

▿ 1 element

▿ 0 : 2 elements

- key : "7A72KACD"

- value : <CKServerChangeToken: 0x600000546500; data=AQAAAAAAAAAIf/////////9qgapowFdF0b2yxdsEOx/U>

Why is this happening?

Maybe it's something related to your another `dictionaryFetchChangeToken`, `UserDefaults.dictionaryFetchChangeToken`.

Please show the definition of it, and the full code of your latest definition of `CloudKitFetchChangeToken.dictionaryFetchChangeToken`.

I think both of your solutions are right, I tried both of them, an the previous error do not arise again.

By the way this is the code of UserDefaults.dictionaryFetchChangeToken.

import Foundation

struct UserDefaultsKeys {
    static let dictionaryFetchChangeToken = "dictionaryFetchChangeToken"
}

extension UserDefaults {
    var dictionaryFetchChangeToken : Data?  {
        get {
            return  data(forKey: UserDefaultsKeys.dictionaryFetchChangeToken)
        }
        set { set(newValue, forKey: UserDefaultsKeys.dictionaryFetchChangeToken) }
    }
}

Thank you very much.

In fact, `unarchiveTopLevelObjectWithData` is exactly the method I used in a code I wrote 4 months ago.

(Sorry, I shoud have dug it out before I write my first code for you.)

Though, the latter `unarchivedObject(ofClasses:from:)` may be a preferred method when you work with data archived with `requiringSecureCoding: true`. (Maybe that may not be a big issue when you get the archived data only from `UserDefaults`.)

Just that the Apple's documentation is so poor...

Anyway, with more related code given, more easily verified code shown. Thank you.

I will need to spend some time in get deep insights from your reply, to fully understand what is going on.

Thanks again.