NSKeyedArchiving issue

Hey Claude31, it’s nice for me to be helping you for a change (-:

It’s hard to tell exactly what’s going wrong here without know more about the objects in play. However, in general, when you decode something from a secure keyed archive, you have to tell the system what type you’re expecting. That’s the key factor is what makes it secure.

Over the years I’ve helped a bunch of folks with problems like this. All of these threads have code snippets from me that you should find useful:

• Question about including all project classes in ofClasses parameter when using NSKeyedUnarchiver.unarchivedObject(ofClasses:from:)
• Fragment large size data sent and received using NSKeyedArchiver.archivedData in GameCenter
• Unarchiving an object with custom classes
• XPC, Swift, ObjC, and arrays
• NSKeyedUnarchiver decodeObjectOfClasses failed
• NSKeyedUnarchiver decodeObjectOfClasses failed
• 'unarchiveTopLevelObjectWithData' was deprecated Use unarchivedObject(ofClass:from:) instead
• NSkeyedArchiver fails when trying to archive subclass objects

If you’re still stuck, distill your problem into a test case that I can run, reply here with that, and I’ll take a deeper look.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"

Hey Quinn, thanks for all the material.

I realize that I have a basic issue in my code.

data is not loaded.

In the previous version, archiver had a connection to data

let archiver = NSKeyedArchiver(forWritingWith: data)

That's no more the case, so data is empty, hence the problems.

    let data = NSMutableData()
    let archiver = NSKeyedArchiver(requiringSecureCoding: true)
    archiver.encode(myObject, forKey: theKey)
    archiver.encode(myObject2, forKey: theKey2)
    archiver.finishEncoding()
    do {
        try data.write(to: an uRL, options: []) // data is empty of course !
    } catch {
     }

So should I replace:

    archiver.encode(myObject, forKey: theKey)
    archiver.encode(myObject2, forKey: theKey2)
    archiver.finishEncoding()
    do {
        try data.write(to: anURL, options: []) // So object and object2 are on file

with

    let data = try! NSKeyedArchiver.archivedData(withRootObject: myObject, requiringSecureCoding: true)
    let data2 = try! NSKeyedArchiver.archivedData(withRootObject: myObject2, requiringSecureCoding: true)
    archiver.finishEncoding()

If so, how do I write object and object2 in a single file properly ? Would I have to include all in a single root class ?

Also, when I compare to https://developer.apple.com/forums/thread/759746,

my required init(coder decoder: NSCoder) is different.

   required init(coder decoder: NSCoder) {
        
        super.init() 
        var1 = decoder.decodeObject(forKey: key) as? [someType]
        var2 = decoder.decodeObject(forKey: key2) as? [someType2]
    }

I do not use decodeObject(of:) as in the reference

            let identifier = decoder.decodeObject(of: NSString.self, forKey: "identifier"),
            let codeDataModels = decoder.decodeArrayOfObjects(ofClass: CodeDataModel.self, forKey: "codeDataModels")

Is it OK ?

That's no more the case, so data is empty, hence the problems.

Indeed. The solution is to get the encodedData property:

let archiver = NSKeyedArchiver(requiringSecureCoding: true)
archiver.encode("Hello Cruel World!" as String, forKey: "greeting")
archiver.finishEncoding()
let data = archiver.encodedData
print(data.count)   // 162

I do not use decodeObject(of:) … Is it OK ?

No. A key goal of secure coding is that you should tell the decoder what type you’re expecting. That allows the decoder to apply its own type checking. This is critical in Objective-C, where it’s easy to confuse types. It’s less critical in Swift, where the compiler is much stricter about type checking, but it’s still the right thing to do. So, whenever you decode, aim to use a decodeXyz(…) method that takes type information.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"