Xcode 4.5 complains that the key does not conform to NSCopying

[echoz]

This is with reference to https://github.com/nulayer/NULevelDB/blob/master/Classes/NULDBDB%2BEnumeration.mm#L140.

Xcode 4.5 raises an issue instead of a warning.

Same for me
fixed by casting key to NSCopying protocol, which of course not perfect solution.