Resource Inclusion uses the power of Responders in Rails 3 to enable a macro for specifying that resources rendered as xml or json include associated resources. This may be used in conjunction with Inherited Resources to keep your controllers lean and mean.

Given a model such as:

create_table :users do |t|
  t.string  :login_id
  t.string  :display_name    
  t.string  :email
end

create_table :comments do |t|
  t.text       :text
  t.references :user
end

Our CommentsController need only have the following to include the user’s attributes:

class CommentsController < ApplicationController

  inherit_resources

  include_resources :user

  #  If you like to type, you could have written the following, but you still
  #  would lack the behavior for other actions which return the resources.
  #
  #  def index
  #    index! do |format|
  #      format.xml{  render :xml  => collection.to_xml(  render_options ) }
  #      format.json{ render :json => collection.to_json( render_options ) }
  #    end
  #  end
  #
  #  def show
  #    show! do |format|
  #      format.xml{ render :xml  => resource.to_xml(  render_options ) }
  #      format.xml{ render :json => resource.to_json( render_options ) }
  #    end
  #  end
  #
  #  def render_options
  #    { :include => [:user] }
  #  end
  #

end

Thus /comments/1.xml would render:

<?xml version="1.0" encoding="UTF-8"?> 
<comment> 
  <id type="integer">1</id> 
  <text>This is comment text.</text> 
  <user-id type="integer">1</user-id> 
  <user> 
    <login-id>aperson</login-id> 
    <display-name>A. Person</display-name> 
    <email>a.person@somedomain.com</email> 
    <id type="integer">1</id> 
  </user> 
</comment>

The output for the json format would be analogous.

Resource Inclusion requires Rails 3.

You can let bundler to install Resource Inclusion by adding this line to your application’s Gemfile:

gem 'resource_inclusion', '0.0.1'

And then execute:

bundle install

Add resource_inclusion to your app/controllers/application_controller.rb file (or to any of your other controllers):

class ApplicationController < ActionController::Base

   resource_inclusion

end

Then use the macro to your controllers as shown above.

In this release of Resource Inclusion the macros support no configuration options beyond what you can pass to serializer (#to_xml or #to_json) with the :include option. These options will be passed to the serializer for any action that uses ActionController#respond_with and with all formats, excluding HTML.

For more on #respond_with see:

• apidock.com/rails/ActionController/MimeResponds/respond_with

• davidwparker.com/2010/03/09/api-in-rails-respond-to-and-respond-with/

• railscasts.com/episodes/224-controllers-in-rails-3

Note that this plug-in has no dependency on Inherited Resources and should work just fine without it. That said, I have not tested with in an application which doesn’t use Inherited Resources so I’ll be interested in feedback from users.

Thanks to Jose Valim for pointing me in the right direction and his must-have Inherit Resources plug-in. If are on Rails 3, wish to expose an REST API and are not using this plug-in, you probably writing more code than you should be. See:

• github.com/josevalim/inherited_resources

Feedback is welcome. If you discover any bugs or want to drop a line, file issues on GitHub or contact me personally via GitHub.

Copyright © 2010 John-Mason P. Shackelford

See the attached MIT License.