From: "Jörg Hagmann" <joerg.hagmann@...>
Date: 2008-01-21T19:00:10+09:00
Subject: classes and superclasses

Dear list members,

A beginner's question:

I wrote a simple programme that assembles exams, choosing the questions 
from a database according to certain criteria. The programme does what I 
want, but I realised there are certain basic things I don't understand, 
e.g.:

My programme has classes analogous to class Song and class SongList in 
the pickaxe book (class Question and class QuestionList).
Class QuestionList includes the definition
def length
@questions.length
end

and that, of course, works.

When, instead of that definition, I make class QuestionList a subclass 
of Array (QuestionList < Array), asking for the length doesn't give me 
an error, but returns a length of 0. So "length" doesn't know what to do 
with an instance of QuestionList, although the latter class includes

def initialize
    @questions = Array.new
end
and is now a subclass of "Array".

Why not? Thanks for answers, J�rg

-- 
Prof.Dr.med. J�rg Hagmann-Zanolari
Institute of Biochemistry and Genetics
Centre of Biomedicine, University of Basel
Mattenstrasse 28
CH-4058 Basel
Switzerland
Phone +41 (0)61 267 3565