Why is my transformable Core Data attribute not using my custom NSValueTransformer?

Question

I have a Core Data app with a fairly simple data model. I want to be able to store instances of NSImage in the persistent store as PNG Bitmap NSData objects, to save space.<

Answer 1

It turns out that this is actually a bug in the frameworks. See this post by an Apple employee on the Cocoa-Dev mailing list:

http://lists.apple.com/archives/Cocoa-dev/2009/Dec/msg00979.html