gistfile1.rb

# Encapsulates presentation and representation information for database objects
# by wrapping them in a presentation layer. Proxies data requests to the data object
# itself for transparency.
# 
# Subclasses allow for customization
# 
# ORM-agnostic
# 
# sample use:
# class PostPresenter < PresenterProxy
#   hidden_attribtes += [ :updated_at, :version, :deleted_at ]
# end
# 
# class PostController < ApplicationController
#   def index
#     @posts = Post.all.map(&PostPresenter)
#     
#     respond_to do |format|
#       format.html
#       format.xml { render => @posts.to_xml }
#       format.js  { render => @posts.to_json }
#     end
#   end
#   
#   def show
#     @post = Post.find(params[:id]).map(&PostPresenter)
# 
#     respond_to do |format|
#       format.html
#       format.xml { render => @post.to_xml }
#       format.js  { render => @post.to_json }
#     end    
#   end
#   
# end

class PresenterProxy
  # TODO: better method mask
  instance_methods.each { |meth| undef_method(meth) unless meth =~ /\A__/ }

  @hidden_addributes = [:lock_version]
  class << self; attr_accessor :hidden_attributes; end

  # allows @presented_posts = Post.all.map(&PresenterProxy)
  def self.to_proc
    proc(&method(:new))
  end

  def initialize(delegate_object)
    @delegate = delegate_object
  end

  # FIXME: dependency on Hash#to_xml
  def to_xml
    @delegate.attributes.except(self.class.hidden_attributes).to_xml :root => obj.class.to_s
  end

  # FIXME: dependency on Hash#to_json  
  def to_json
    @delegate.attributes.except(self.class.hidden_attributes).to_json
  end

  # TODO: more intelligent proxying
  def method_missing(meth, *args, &block)
    @delegate.send(meth, *args, &block)
  end

  def respond_to(method)
    @delegate.respond_to?(method) || super
  end

end