Overview of new features in Rails 2.3 followed by a deeper discussion of Rack, Rack Middleware, and creating Metal Endpoints.

1. Rails 2.3
Brian Turnbull
http://brianturnbull.com

2. Templates
rails app
rails app’
template
rails app -m template.rb
rails app -m http://example.com/template
rake rails:template LOCATION=template.rb

3. Templates
# template.rb
gem quot;hpricotquot;
rake quot;gems:installquot;
run quot;rm public/index.htmlquot;
generate :scaffold, quot;person name:stringquot;
route quot;map.root :controller => 'people'quot;
rake quot;db:migratequot;
git :init
git :add => quot;.quot;
git :commit => quot;-a -m 'Initial commit'quot;
Pratik Naik — http://m.onkey.org/2008/12/4/rails-templates

4. Templates
Jeremy McAnally’s Template Library
http://github.com/jeremymcanally/rails-templates/tree/master

5. Engines
Rails Plugins turned to Eleven
Share Models, Views, and
Controllers with Host App
Share Routes with Host App
http://rails-engines.org/news/2009/02/02/engines-in-rails-2-3/

6. Engines
Not Yet Fully Baked
Manually Manage Migrations
Manually Merge Public Assets
http://rails-engines.org/news/2009/02/02/engines-in-rails-2-3/

7. Nested Transactions
User.transaction do
User.create(:username => 'Admin')
User.transaction(:requires_new => true) do
User.create(:username => 'Regular')
raise ActiveRecord::Rollback
end
end
User.find(:all) # => Returns only Admin
http://guides.rubyonrails.org/2_3_release_notes.html

8. Nested Attributes
class Book < ActiveRecord::Base
has_one :author
has_many :pages
accepts_nested_attributes_for :author, :pages
end
http://guides.rubyonrails.org/2_3_release_notes.html

9. Nested Forms
class Book < ActiveRecord::Base
has_many :authors
accepts_nested_attributes_for :authors
end
<% form_for @book do |book_form| %>
<div>
<%= book_form.label :title, 'Book Title:' %>
<%= book_form.text_field :title %>
</div>
<% book_form.fields_for :authors do |author_form| %>
<div>
<%= author_form.label :name, 'Author Name:' %>
<%= author_form.text_field :name %>
</div>
<% end %>
<% end %>
<%= book_form.submit %>
<% end %>
http://guides.rubyonrails.org/2_3_release_notes.html

10. Dynamic and Default Scopes
## id Integer
## customer_id Integer
## status String
## entered_at DateTime
class Order < ActiveRecord::Base
belongs_to :customer
default_scope :order => 'entered_at'
end
Order.scoped_by_customer_id(12)
Order.scoped_by_customer_id(12).find(:all,
:conditions => quot;status = 'open'quot;)
Order.scoped_by_customer_id(12).scoped_by_status(quot;openquot;)
http://guides.rubyonrails.org/2_3_release_notes.html

11. Other Changes
Multiple Conditions for Callbacks
HTTP Digest Authentication
Lazy Loaded Sessions
Localized Views
and More!
http://guides.rubyonrails.org/2_3_release_notes.html

12. Rails 2.3

13. Rails Metal

14. SPEED
Simplicity

15. Metal Endpoint
## app/metal/hello_metal.rb
class HelloMetal
def self.call(env)
if env[quot;PATH_INFOquot;] =~ /^/hello/metal/
[200, {quot;Content-Typequot; => quot;text/plainquot;}, [quot;Hello, Metal!quot;]]
else
[404, {quot;Content-Typequot; => quot;text/htmlquot;}, [quot;Not Foundquot;]]
end
end
end
http://soylentfoo.jnewland.com/articles/2008/12/16/rails-metal-a-micro-framework-with-the-power-of-rails-m

16. Equivalent Controller
## app/controllers/hello_rails_controller.rb
class HelloRailsController < ApplicationController
def show
headers['Content-Type'] = 'text/plain'
render :text => 'Hello, Rails!'
end
end
http://soylentfoo.jnewland.com/articles/2008/12/16/rails-metal-a-micro-framework-with-the-power-of-rails-m

17. Sinatra!
require 'sinatra'
Sinatra::Application.set(:run => false)
Sinatra::Application.set(:environment => :production)
HelloSinatra = Sinatra::Application.new unless defined? HelloSinatra
get '/hello/sinatra' do
response['Content-Type'] = 'text/plain'
'Hello, Sinatra!'
end
http://soylentfoo.jnewland.com/articles/2008/12/16/rails-metal-a-micro-framework-with-the-power-of-rails-m

18. Rack
Object.call(env)
[status,
headers,
response]

19. Metal Endpoint
## app/metal/hello_metal.rb
class HelloMetal
def self.call(env)
if env[quot;PATH_INFOquot;] =~ /^/hello/metal/
[200, {quot;Content-Typequot; => quot;text/plainquot;}, [quot;Hello, Metal!quot;]]
else
[404, {quot;Content-Typequot; => quot;text/htmlquot;}, [quot;Not Foundquot;]]
end
end
end

20. Rack Middleware in Rails
Rails Dispatcher
call(env) [s,h,r]
Middleware
call(env) [s,h,r]
Middleware
call(env) [s,h,r]
Web Server

21. Rack Middleware in Rails
% rake middleware
use Rack::Lock
use ActionController::Failsafe
use ActionController::Session::CookieStore
use Rails::Rack::Metal
use ActionController::RewindableInput
use ActionController::ParamsParser
use Rack::MethodOverride
use Rack::Head
use ActiveRecord::QueryCache
run ActionController::Dispatcher.new

22. Rack Middleware in Rails
% rake middleware
use Rack::Lock
use ActionController::Failsafe
use ActionController::Session::CookieStore
use Rails::Rack::Metal
use ActionController::RewindableInput
use ActionController::ParamsParser
use Rack::MethodOverride
use Rack::Head
use ActiveRecord::QueryCache
run ActionController::Dispatcher.new

23. Django > Rails?
## lib/middleware/django_middleware.rb
class DjangoMiddleware
def initialize(app)
@app = app
end
def call(env)
status, headers, response = @app.call(env)
new_response = []
response.each do |part|
new_response << part.gsub(/Rails/, 'Django')
end
[status, headers, new_response]
end
end
## config/environment.rb
config.middleware.use DjangoMiddleware

24. http://github.com/bturnbull/bturnbull-metal-demo