application_controller.rb

class ApplicationController < ActionController::Base
  extend AttributeViewable
end

attribute_viewer.rb

module AttributeViewer
  def attr_viewable(*names)
    names.each do |name|
      attr_accessor name
      helper_method name
      private "#{name}=".to_sym
    end
  end
end

index.html.erb

<table>
<% messages.each do |message| %>
  <tr>
    <td><%= message.subject %></td>
    <td><%= message.body %></td>
    <td><%= link_to 'Show', message %></td>
    <td><%= link_to 'Edit', edit_message_path(message) %></td>
    <td><%= link_to 'Destroy', message, confirm: 'Are you sure?', method: :delete %></td>
  </tr>
<% end %>
</table>

messages_controller.rb

class MessagesController < ApplicationController
  attr_viewable :message, :messages

  def index
    self.messages = Message.all
  end
end

@myobie you could mix in a module on each request. So something like:

class MessagesController < ApplicationController
  def index
    extend Module.new {
      attr_accessor :messages
    }

    self.messages = IndexContainer.new(Message.all)
  end
end

But I strongly advise against doing that. It breaks method caches which will slow method lookup on every request, and couples your code with the fact that the controller is a new instance on every request.

Usage of a context (or container, or presenter, or whatever you want to call it) object allows you to:

• test behavior of the container outside of your controller (you don't need to write a functional test to test the Container)
• decouple the view from the controller (you could test the view without instantiating a controller)
• get NoMethodErrors raised exactly at the point where the error occurred (rather than waiting for the nil to be used)