CoreData Transformable Types and SecureCoding

Question

I have a CoreData entity with a transformable property data that stores an NSDictionary. All of the classes inside the dictionary conform to NSSecureCoding

I have been getting many instances of this warning : 'NSKeyedUnarchiveFromData' should not be used to for un-archiving and will be removed in a future release

In trying to clean up the warning and future-proof my app, but I am running into a lot of trouble.

My understanding is that using NSKeyedUnarchiveFromData as the transformer in my data properties attribute should work, since the top level class is a dictionary and all of the contents conform to NSSecureCoding.

However, my data dictionary is now coming back as NSConcreteMutableData so I cannot access the data in it.

I have also tried creating a custom value transformer with additional allowedTopLevelClasses, but that hasn't helped, and again, the topLevel type is an NSDictionary, which should be allowed.

Thank you for any guidance.

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Posted by

benkamen

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Answer 1

Thanks. The relevant piece that I was missing is that it's not just the literal topLevelClasses that need to be registered with the NSSecureUnarchiveFromDataTransformer, but also any classes contained in the transformable if it's a collection. Therefore, if my NSDictionary has a custom class inside it, I need to register a subclass of NSSecureUnarchiveFromDataTransformer to allow that class.

@objc
class DataTransformer: NSSecureUnarchiveFromDataTransformer {
 
    static let name = NSValueTransformerName(rawValue: String(describing: DataTransformer.self))

    @objc(registerValueTransformer)
    public static func register() {
         let transformer = DataTransformer()
        print(DataTransformer.allowedTopLevelClasses)
         ValueTransformer.setValueTransformer(transformer, forName: name)
     }
    
    override class var allowedTopLevelClasses: [AnyClass] {
        var topLevelClasses = super.allowedTopLevelClasses
        let myClasses = [MyClass.self, MyOtherClass.self]
        topLevelClasses.append(contentsOf: myClasses)
        return topLevelClasses
    }

}

Posted by

benkamen

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Answer 2

You need to add an example of your code.

Posted by

Easiwriter

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Answer 3

Easiwriter wrote:

You need to add an example of your code.

Yes, that’d help.

To get you started, check out the example of secure coding in Objective-C in this thread.

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

Posted by

eskimo

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Answer 4

Thanks. The relevant piece that I was missing is that it's not just the literal topLevelClasses that need to be registered with the NSSecureUnarchiveFromDataTransformer, but also any classes contained in the transformable if it's a collection. Therefore, if my NSDictionary has a custom class inside it, I need to register a subclass of NSSecureUnarchiveFromDataTransformer to allow that class.

@objc
class DataTransformer: NSSecureUnarchiveFromDataTransformer {
 
    static let name = NSValueTransformerName(rawValue: String(describing: DataTransformer.self))

    @objc(registerValueTransformer)
    public static func register() {
         let transformer = DataTransformer()
        print(DataTransformer.allowedTopLevelClasses)
         ValueTransformer.setValueTransformer(transformer, forName: name)
     }
    
    override class var allowedTopLevelClasses: [AnyClass] {
        var topLevelClasses = super.allowedTopLevelClasses
        let myClasses = [MyClass.self, MyOtherClass.self]
        topLevelClasses.append(contentsOf: myClasses)
        return topLevelClasses
    }

}

Posted by

benkamen

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CoreData Transformable Types and SecureCoding

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