A fresh Rails 3.0 app with generators, Rack::Bug with Orchestra and Thorfile examples.
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Third Rails - Rails 3.0 Sample Application

The original Third Rails was created by @josevalim and it is available here:


It has very specific goals:

  • showcase Rails 3.0 new folder structure

  • demonstrate the usage of custom generators

This application is fully self-contained. In this fork I've done:

  • vendorized all needed gems

  • updated the railties files to the latest version

Gem Bundler

If you want to use the newest gem dependency manager support, you have to install a separate gem called Bundler, from @wycatz, available here: github.com/wycats/bundler

sudo gem install bundler

All the necessary gems are already vendorized under vendor/gems and if the gem has executables, they will be at bin/, such as the 'spec', 'rails' commands and others. Check out the next section.

Using Third Rails

There are 2 ways to use this project: with shared gems, or local gems.

The simple approach right now is to just do this:

git clone git://github.com/akitaonrails/third_rails.git

You need to have the Rails source project somewhere as well:

git clone git://github.com/rails/rails.git
cd rails
git submodule init
git submodule update

Now edit the Gemfile inside the 'third_rails' project you just cloned and change the variable rails_source_path in the first line to the correct path of your Rails source project. After that you can do:

cd third_rails
gem bundle

This will vendorize all needed gems inside the project's vendor/gems folder so everything works smoothly. You need to install the Bundler gem, see the previous section.

Talking to @josevalim he clarified what would be the easy way to just test this app and to create your own test bed. Again, you will need the Rails source project:

git clone git://github.com/rails/rails.git
cd rails
git submodule init
git submodule update
gem bundle

Bundler will create a vendor/gems folder inside the Rails source project, then you need to edit the config/boot.rb, specifically this first line:

environment = File.expand_path('../../vendor/gems/environment', __FILE__)

Replace the path for the correct path to your gems folder inside the Rails project. If you do this for every Rails 3 project, you will reuse the same gems. For example, my Rails project is in this path: ~/Sites/rails/rails/vendor/gems/environment

But there is a caveat: it will override the Gemfile in your project. So you won't be able to have project specific gems. So this is not good enough for normal development, but will do to quickly create a test project.

Rails 3.0 First Impressions (by @AkitaOnRails)

There are new files available in the structure:

  • Gemfile - that's where you configure all the needed gems

  • config.ru - Rails fully supports Rack, and from now on, even script/server bootstraps using Rack

The good old config/environment.rb is now lighter and it basically depends on a new file called config/application.rb. So, whatever you used to do in environment.rb you should now to at application.rb

All the old 2.x Rails generators will not work, so Rspec, Cucumber, and any other gem that supported generators will have to rewrite them to the new style which depends on Thor. In this project you can see how they will look like: take a look in lib/generators for examples. There you will find RSpec and DataMapper custom generators.

If you want to use this project to start your own new Rails 3 project, don't simply copy it. The new config/application.rb file declared a new class called ThirdRails, which is the name of your application, and several other files expect to find this constant. So you need to update the following files to the new constant if you change the name of the app:


It is well known that the Routes engine received a lot of attention and it also sports a refined DSL. Check out config/routes.rb as there are examples of usage. Basically, they rely on blocks instead of hashes now, so the old style would be:

map.resources :posts, :member => { :first => :get }

And the new style becomes:

resources :posts do
  member do
    get :first

Much cleaner if you ask me. Also don't forget the the Controller was also heavily revised and now supports @josevalim's Inherited Resources style. Check out his plugin to learn it today:


Just for now, there seems to be a glitch in the new Routing DSL. If I do map.resources :people everything works correctly. If I use the new resources :people, then pluralization gets messed up and I end up having routes like /peoples. It's probably gonna be fixed before release.

Rails now will bundle other 3rd party gems. It already had tztime for Time Zone support, Rack, and now Thor for the generators. Another interesting one is “Arel”, described as “Relational Algebra for Ruby” or a way to write cleaner and more expressive SQL queries in Ruby style. Worth checking out its documentation. I didn't peek into ActiveRecord and ActiveModel but I bet they are replacing its own internal SQL handling for Arel:


Rails is highly modularized now. You have the bare bone “Rails Metal” and you can even build a small Sinatra-like micro-framework as @wycatz explained:


ActiveRecord and ActiveResource have also received a lot of love and the result is the extraction of ActiveModel as a separate project so you can build Model-like classes that do not rely neither on a database table or web service and still have all the validations, filters and other goodies.

If you're a DataMapper, Sequel or other ORM developer, take a look into the ActiveModel::Lint::Tests module inside the Rails/ActiveModel project. They delineate the requirements for you to create a thin adapter layer for your ORM so Rails can transparently use it.

You want to start a project from scratch

When Rails 3 gets released you can simply do:

sudo gem install rails
rails my_project

But, while it doesn't happen, you need to go straight to the source, so, again:

git clone git://github.com/rails/rails.git
cd rails
git submodule init
git submodule update

From within the Rails project folder, you can create a new project like this:

ruby railties/bin/rails /path/to/new/project

Now, it is a good time to change your Rails Gemfile content for this:

rails_source_path = "/Users/akitaonrails/Sites/rails/rails/"

gem "rake", ">= 0.8.7"
gem "mocha", ">= 0.9.8"

gem "rails", "3.0.pre", :path => "#{rails_source_path}railties"
%w(activesupport activemodel actionpack actionmailer activerecord activeresource).each do |lib|
  gem lib, '3.0.pre', :path => "#{rails_source_path}#{lib}"

# AR
gem "arel", "0.2.pre", :git => "git://github.com/rails/arel.git"
gem "sqlite3-ruby", ">= 1.2.5"

# AP
gem "rack", "1.0.1", :git => "git://github.com/rails/rack.git"

Again, change the rails_source_path to the path of the Rails source project you just cloned. Once you do it, you can choose to vendorize these gems into your project like this:

gem bundle

Do not forget to install the bundler gem first, as I mentioned before. This will vendorize the gems inside your own project. If you don't want to duplicate your gems all the time, read the 'Using Third Rails' section above to understand how to have a shared gems repository within your Rails source project.

If everything goes fine, you should be able to start using the usual Rails commands:


This should make you prepared to start learning Rails 3. And if you are a Gem or Rails Plugin developer: NOW is the time to start updating and testing your projects!! Remember: a lot has changed under the hoods, so if your project rely on any monkey-patching you must re-test it against Rails 3 because it will most certainly break. If your project as generators, learn how to rewrite them.



There is a custom generator for DataMapper to illustrate how other ORMs can also have Rails-like generators. Problem is, up to this point it is not yet clear to me how to Wrap DataMapper as an ActiveModel object. There will be a clear way to do it, but I have to research more how (anyone?)

I've also added a still in development new plugin called Responder, form the Plataforma Tec guys. This is a scaffold generator to create thinner controllers using respond_with instead of the usual more verbose respond_to version that is the Rails default.

The included example controller was already generated that way and if you want to use this new generator, do this:

git submodule update --init