gistfile1.rb

# app/presenters/product_presenter.rb
class ProductPresenter < Presenter
  def description
    # ...
  end
end

# app/presenters/person_presenter.rb
class PersonPresenter < Presenter
  def name
    "Caro #{name}"
  end
end

# app/presenters/presenter.rb
class Presenter < SimpleDelegator
  attr_reader :object
  
  def initialize(object)
    @object = object
    
    __setobj__ @object
  end
  
  def eql?(target)
    target == self || object.eql?(target)
  end
  
  private

  def helpers
    ApplicationController.helpers
  end

  def routes
    ApplicationController.routes
  end
end



# ========= Controllers =========== #

# app/controllers/products_controller.rb
class ProductsController < ApplicationController
  def show
    @product = Product.find(params[:id]).present
  end
end

# app/controllers/people_controller.rb
class PeopleController < ApplicationController
  def show
    @person = Person.find(params[:id]).present
  end
end


# config/initializers/activerecord.rb
ActiveRecord::Base.class_eval do
  def present
    "#{self.class.to_s}Presenter".constantize.new(self)
  end
end