From: ara.t.howard@...
Date: 2006-07-07T12:47:41+09:00
Subject: Re: quick metaprogramming question: collecting arguments across calls

On Fri, 7 Jul 2006, William Morgan wrote:

> Hi all,
>
> Quick question: is there a better way to write Foo.contains below?
> Forcing the lexical scoping like this feels wrong.
>
> class Foo
>  def self.contains *o
>    @contents ||= []
>    @contents += o
>    contents = @contents
>    define_method(:contents) { contents }
>  end
> end
>
> class Bar < Foo
>  contains :goat, :boat
>  contains :stoat
> end
>
> p Bar.new.contents # => [:goat, :boat, :stoat]

if the behaviour is useful - abstract it:


   harp:~ > cat a.rb
   module Container
     module ClassMethods
       def contents() @contents ||= [] end
       def contains(*list) contents.push *list.flatten end
     end
     def contents() self.class.contents end
     def self.included other
       other.extend ClassMethods
       super
     end
   end

   class Foo
     include Container
   end

   class Bar < Foo
    contains :goat, :boat
    contains :stoat
   end

   p Bar.new.contents # => [:goat, :boat, :stoat]


   harp:~ > ruby a.rb
   [:goat, :boat, :stoat]

regards.

-a
-- 
suffering increases your inner strength.  also, the wishing for suffering
makes the suffering disappear.
- h.h. the 14th dali lama