I am describing a problem for which it took me quite some time to learn the answer.
The "GenericKeychain" example is a good start at providing a wrapper for sharing keychain data between applications when using the accessGroup in the init.
However, implementing this in my app yielded an obscure error code (which took forever to locate) -25243, which means: No access control.
I ran Apple's example app (GenericKeychain) on my iPad only to get the same error. Huh?
Does Apple's documentation fail to deliver on what is necessary to accomplish this?
After some (a lot of) digging throughout the web, I found the answer. The access Group that you use when constructing your KeychainItemWrapper class must ALSO be specified in each of your application's Entitlements.plist file in the "keychain-access-groups" section.
It seems almost obvious now that I see "keychain-access-groups". However, I had no idea to even look there. Hope this helps others.