Is it true that I don't have to create my own NSValueTransformer subclass if my object applies to the NSCoding protocol?

Question

i.e. lets say I want to store a custom data type in Core Data. The documentation claims that the default NSValueTransformer is an NSKeyedUnarchiveFromDataTransformer thing, so I guess if the class of the object I want to store conforms already to that NSCoding protocol, I don't need to bother about making a custom NSValueTransformer? Is that correct?