encodeConditionalObject(_:forKey:)
An encoding method for subclasses to override to conditionally encode an object, preserving common references to it, only if it has been unconditionally encoded.
Declaration
func encodeConditionalObject(_ object: Any?, forKey key: String)Discussion
Subclasses must override this method if they support keyed coding.
The encoded object is decoded with the decodeObject(forKey:) method. If objv was never encoded unconditionally, decodeObject(forKey:) returns nil in place of objv.