From: nobu.nakada@...
Date: 2000-02-20T20:57:54+09:00
Subject: [ruby-list:20876] active attribute

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なかだです。

  あぅ。さっきのは subject 間違ってます(;_;)。こっちが active
attribute、あっちは aliasing module のはずでした。

  で、リサイクル第２段。実は active attribute って何を指してるか
よく分かってなかったりしますが、こういうもんでしょうか。

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class Module
  class ActiveAttr < Module
    Separator = '.'.freeze
    ThreadKey = nesting[0].to_s.intern

    def self.new(obj, name, &defs)
      String === name or name = name.id2name
      opref, owner = Thread.current[ThreadKey]
      prefix = opref.to_s + name + Separator
      actor = super()
      adaptor = Class.new(Adaptor)
      begin
	Thread.current[ThreadKey] = [prefix, adaptor]
	actor.adapt(adaptor, prefix, &defs)
	adaptor.bind(owner || obj, name, (opref ? '@owner' : 'self'))
      ensure
	Thread.current[ThreadKey] = ([opref, owner] if opref)
      end
      actor
    end

    def adapt(adaptor, prefix, &defs)
      module_eval(&defs)
      im = instance_methods - Module.instance_methods
      im.each do |m|
	alias_method(prefix + m, m)
	remove_method(m)
      end
      adaptor.prefix(prefix, im)
    end

    class Adaptor
      def self.prefix(pref, meths)
	meths.each do |m|
	  module_eval "def #{m}(*args) @owner.__send__(#{(pref + m).intern}, *args) end"
	end
	self
      end

      def self.bind(owner, name, msg)
	adaptor = self
	owner.module_eval %{
	  @#{name} = adaptor
	  def #{name}
	    @#{name} ||= self.type.instance_eval {@#{name}}.new(#{msg})
	  end
	}
      end

      def initialize(owner)
	@owner = owner
      end
    end
  end

  def active_attr(name, &defs)
    include(ActiveAttr.new(self, name, &defs))
  end
end

if __FILE__ == $0
  class A
    attr_reader :v

    def initialize
      @v = []
    end

    active_attr :x do
      def []=(*args)
	v = args.pop
	@v[*args] = v
      end
      def [](*args)
	@v[*args]
      end
      def q
	@v
      end

      active_attr :y do
	attr_accessor :v
      end
    end
    active_attr :y do
      # distinguished to x.y, so y.v causes exception
    end
  end

  a = A.new
  # shuffle test data
  s = (0...10).to_a
  while i = s.size.nonzero?
    a.v << s[i = rand(i)]
    s[i, 1] = nil
  end

  require 'ok'
  ok = Check['active attribute']
  ok[a.x.q == a.v]
  ok[a.x.y.v == a.v]
  ok[begin a.y.v; nil; rescue NameError; $! end]
end

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-- 
そうだ 強気に ちょっと インチキに☆彡
    中田 "Bugるくらいがちょうどいいかも;-)" 伸悦

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