I'm updating an app and discovered that with iOS 14 and core data, when using a transformable attribute, I can no longer use the standard value transformer and have to write my own. That was fairly straightforward and implementing it was also straightforward.

In the core data definition you have to name the value transformer and this is where my problem begins. In order to support iOS versions earlier than 12 (I need to go back to 10), I need to subclass from the ValueTransformer class. In iOS 12 I can use NSSecureUnarchiveFromDataTransformer (which inherits from ValueTransformer) and beginning with iOS 14 this class is required to sublcass from otherwise the compiler complains its not secure.

How can I name the value transformer type in core data to support iOS 10 and 11 and dynamically, at run time, switch to the other value transformer?