gistfile1.rb

# A very simplistic "presenter" implementation.  It works by simply extending
# an object with a presenter module

# presenter.rb
module Presenter
  def self.for_class(klass)
    Object.const_get(klass.name + 'Presenter') rescue nil
  end
  
  # extends the given record with the presenter module for the object type
  # (i.e. instance of Article will try to extend with ArticlePresenter)
  def self.for(record)
    (presenter = for_class(record.class)) ? record.extend(presenter) : record
  end
end

# article.rb
class Article < ActiveRecord::Base
end

# article_presenter.rb
module ArticlePresenter
  def published_at
    published_at.eztime(':day :nmonth :year')
  end
end

# usage
article = Presenter.for(Article.find(1))
article.published_at   # => 28 November 2009
url_for(article)       # => /articles/1