From: r2d2@... (Niklas Frykholm) Date: 2001-05-26T18:10:04+09:00 Subject: [ruby-talk:15745] Re: Ruby Programming Practice >But in a general Ruby programming view, where one programmer >is controlling all the files, is it good practice for a superclass to >use a method (or instance variable) defined by a derived class? >This does not seem to follow from the library designer view. I would probably put a placeholder in the superclass just to remind myself that the method needs to be implemented in all subclasses. class Shape def area raise "Shape#area not defined in subclass" end end -- Niklas