From: ara.t.howard@...
Date: 2006-03-13T09:16:30+09:00
Subject: Re: [RCR] abstract method in Ruby

On Mon, 13 Mar 2006, Yukihiro Matsumoto wrote:

> Hi,
>
> In message "Re: [RCR] abstract method in Ruby"
>    on Sun, 12 Mar 2006 16:38:44 +0900, "kwatch" <kwa@kuwata-lab.com> writes:
>
> |The following code itself describes that method each() is abstract.
> |It's more descriptive.
> |
> |  module Enumerable
> |    abstract_method :each
> |    def map
> |      arr = []
> |      each { |elem| arr << yield(elem) }
> |      arr
> |    end
> |  end
>
> I'm afraid that it doesn't work for some cases, for example:
>
>  class Base
>    def each
>      ...
>    end
>  end
>
>  class Derived < Base
>    include Enumerable
>    ...
>  end
>
> The abstract "each" method defined in Enumerable overrides the "each"
> in the Base class.  I'm not against the idea of abstract (or deferred)
> method, but sometimes it's not that simple.

how about something very simple?  i use this in my own code

   class Module
     def abstract_method m
       define_method(m){|*a| raise NotImplementedError}
     end
   end

   module Interface
     abstract_method "foo"
     abstract_method "bar"
   end

   class C
     include Interface
   end


it's quite nice for the rdocs.

regards.

-a

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