From: Matthew Smillie <M.B.Smillie@...>
Date: 2005-11-14T07:33:55+09:00
Subject: Re: Heirarchy Troubles

On Nov 13, 2005, at 22:12, CBlair1986 wrote:

> Hello all. I've got a somewhat unique problem, I think. I have a list
> of classes planned out, with the attributes needed for them and
> everything else, but I want to figure out how the classes should  
> relate
> to one another, so that I don't need to needlessly repeat myself.

This isn't unique at all, but is in fact one of the defining aspects  
of all object-oriented design.  You can learn about it in the Pickaxe  
here: http://www.whytheluckystiff.net/ruby/pickaxe/html/tut_classes.html


> For instance, say I have the classes planned as such:
> class Apple
>   attr_accessor :taste, :type, :flavor, :flesh, ...
> end
> class Orange
>   attr_accessor :taste, :type, :flavor, :peel, ...
> end
> and so on.

class Fruit
   attr :taste, :flavor, ...
end

class Apple < Fruit
   attr :something_unique_about_apples
end

class Citrus < Fruit
   def prevents_scurvy?
     true
   end
end

class Orange < Citrus
   # has everything from Fruit and Citrus and whatever's unique about  
Oranges
end

class Lime < Citrus
   # has everything from Fruit and Citrus and whatever's unique about  
Limes
end


For simple, every-day objects, this is a fairly straight-forward  
process: Take an apple, and take an orange.  Make a list of the  
properties of the apple you want to represent, and a similar list for  
the orange.  When you want to represent the same thing for both of  
the objects, make a superclass for them for those attributes/methods  
(Fruit, Citrus).