http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/ Extra Decoratorで、Decoratorの連鎖をしてみたサンプル

extradeco.rb

require "delegate"
require "optparse"

# Socail Logic
class Facebook
  def self.post(title, user)
    p "post to facebook, title: #{title}, user: #{user}"
  end
end

class Twitter
  def self.post(title, user)
    p "post to twitter, title: #{title}, user: #{user}"
  end
end

class Plus
  def self.post(title)
    p "post to plus, title: #{title}"
  end
end

# Model
class Comment
  attr :title
  attr :author
  def initialize(title, author)
    @title = title
    @author = author
  end
  def save
    p "save to comment model, title: #{title}, author: #{author}"
  end
end

# Decorator
class FacebookCommentNotifier < SimpleDelegator

  def initialize(comment)
    @comment = comment
    super
  end

  def save
    @comment.save && post_to_wall
  end

private

  def post_to_wall
    Facebook.post(@comment.title, @comment.author)
  end
end

class TwitterCommentNotifier < SimpleDelegator
  def initialize(comment)
    @comment = comment
    super
  end

  def save
    @comment.save && post_to_wall
  end

private

  def post_to_wall
    Twitter.post(@comment.title, @comment.author)
  end
end

class PlusCommentNotifier < SimpleDelegator
  def initialize(comment)
    @comment = comment
    super
  end

  def save
    @comment.save && post_to_wall
  end

private

  def post_to_wall
    Plus.post(@comment.title)
  end
end

# main
if __FILE__ == $0
  title = ""
  user = ""
  params = Hash.new
  opt = OptionParser.new
  opt.on('-t', '--title=VAL') {|v| title = v}
  opt.on('-u', '--user=VAL') {|v| user = v}
  opt.on('--[no-]fb') {|v| params[:fb] = v}
  opt.on('--[no-]tw') {|v| params[:tw] = v}
  opt.on('--[no-]pl') {|v| params[:pl] = v}
  opt.parse!(ARGV)

  @comment = Comment.new(title, user)
  if params[:fb]
    @comment = FacebookCommentNotifier.new(@comment)
  end
  if params[:tw]
    @comment = TwitterCommentNotifier.new(@comment)
  end
  if params[:pl]
    @comment = PlusCommentNotifier.new(@comment)
  end

  if @comment.save
    p "Your comment was posted."
  else
    p "Your comment can't post"
  end
end