Re: I have a problem with D

[Bienlein via Digitalmars-d]

You can make use of the visitor pattern. The user that created 
some subclass then only needs to fill the visitor method with 
some stuff and that's it. The visitor was already initialized 
when created which happened before it was handed in to the 
visitor method of the subclass as a method parameter and things 
are fine.

-- Bienlein