Encodes a reference to a given object and associates it with a key only if it has been unconditionally encoded elsewhere in the archive.
- iOS 2.0+
- macOS 10.2+
- Mac Catalyst 13.0+
- tvOS 9.0+
- watchOS 2.0+
The object to encode.
The key with which to associate the encoded value. This value must not be
This method is effective only if you’ve previously archived this object with this key by calling