How to implement the unarchiver delegate for overw

I have 2 Targets of my IOS-App : MYAPPTARGET_1 & MYAPPTARGET_2
MYAPPTARGET_1 is writing a Stream to a BLOB using NSKeyedArchiver
MYAPPTARGET_2 is reading a Stream from a BLOB using NSKeyedUnarchiver

When unarchiving the Stream from the BLOB in my MYAPPTARGET_2, I get the Error: 016-01-18 15:01:38.541 WorldHistoryAtlasTest[598:9405] * Terminating app due to uncaught exception 'NSInvalidUnarchiveOperationException', reason: '* -[NSKeyedUnarchiver decodeObjectForKey:]: cannot decode object of class (MYAPPTARGET_1.MapTheme) for key (rootobject);

So it seemes to be obviously encoded with a prefix of MYAPPTARGET_1 and is not readable from MYAPPTARGET_2.

So I got a hint for overcome this in another STACKOVERFLOW Answer to use a delegate unarchiver to overwrite the Classname. But I am not able to implement this:

func unarchiver(unarchiver: NSKeyedUnarchiver, cannotDecodeObjectOfClassName name: String, originalClasses classNames: [String]) -> AnyClass? {
    print("ClassName is " + name);
    return nil; // WHAT TO DO , TO OVERWRITE THE CLASS NAME.
}

 var mykeyedunarchiver:NSKeyedUnarchiver=NSKeyedUnarchiver(forReadingWithData: data!);
 mykeyedunarchiver.delegate = self;
 let temp=mykeyedunarchiver.decodeObjectForKey("rootobject")

I have an App with targetname MYAPPTARGET_1 and I store some data as blob using the NSKeyedArchiver feature.

Then later with a second Apps-Target named MYAPPTARGET_2 I try to read the data again. Load from the BLOB stored in the DB.

I would be so happy if someone could give me a practical hint on this.

the following is enough:

class MyObject: NSObject, NSCoding {...}
let my = MyObject()

// archive
NSKeyedArchiver.setClassName("MyObject", for: MyObject.self)
let data = NSKeyedArchiver.archivedData(withRootObject: r)

// unarchive
NSKeyedUnarchiver.setClass(MyObject.self, forClassName: "MyObject")
let _ = NSKeyedUnarchiver.unarchiveObject(with: data)

this helped me to exchange custom objects between a mac-app and an iphone app