Custom wrapper for Net classes

[juancentro]

I can't get a clear definition from the vignette on how to write a custom wrapper for a Net class to R. I have a class that is similar to a variant, and I want to be able to specify how it should be handled, depending on some field that this class has (which indicates the real type).
Can I just pass an instance of my class to R and let R do the job (by checking the type in R). Or R just accepts an standard set of types (double, string, etc)?