On 18 Mar 2022, at 07:23, Ben Kennedy <ben-groups@...> wrote:

On 16 Mar 2022, at 11:54 pm, Gerriet M. Denkmann <gerriet@...> wrote:

So: How to explicitly include NSNumber into the client allowed classes set ?

Have you tried using secure [de]coding?

https://developer.apple.com/documentation/foundation/nssecurecoding
https://developer.apple.com/documentation/foundation/nscoder/2292944-decodeobject#

replacing in:
override func decodeRestorableState(with coder: NSCoder)

all:
languageFilter = coder.decodeObject(forKey: "languageFilter”)
with:
languageFilter = coder.decodeObject(of: [NSString.self], forKey: "languageFilter”)

solved the problem.

Thanks for your help!

Gerriet