From: Sean O'Halpin <sean.ohalpin@...>
Date: 2005-10-27T19:32:24+09:00
Subject: Re: Cleaner syntax for .map (is there already a way, or ruby2 idea?)

On 10/27/05, nobuyoshi nakada <nobuyoshi.nakada@ge.com> wrote:
> What about:
>
>  module Mappable
>    class Mapper
>      def initialize(obj)
>        @obj = obj
>      end
>      def method_missing(meth, *args, &block)
>        @obj.map {|i| i.send(meth, *args, &block)}
>      end
>    end
>    def self.included(klass)
>      super
>      aref = klass.instance_method(:[])
>      klass.module_eval do
>        define_method(:[]) do |*idx|
>          if idx.empty?
>            Mapper.new(self)
>          else
>            aref[*idx]
>          end
>        end
>      end
>    end
>  end
>
>  class Array
>    include Mappable
>  end
>
>  a = %w[a b c]
>  p a[].upcase
>
> --
> Nobu Nakada
>
As always, there's something magical about your code! Unfortunately,
it makes pp blow up for one ;)

For a similar purpose, I use this - not as slick but simple and
understandable. Doesn't handle the nesting though.

module Enumerable
  def where(&block)
    self.select{|x| x.instance_eval(&block) }
  end
  def project(&block)
    self.map{|x| x.instance_eval(&block) }
  end
end

as in

  depts.where{ name == "Apps" }.project{ people.project{ name } }

Regards,

Sean