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Ruby on Rails 3.1 Release Notes

Highlights in Rails 3.1:

These release notes cover only the major changes. To learn about various bug fixes and changes, please refer to the changelogs or check out the list of commits in the main Rails repository on GitHub.


Upgrading to Rails 3.1

If you're upgrading an existing application, it's a great idea to have good test coverage before going in. You should also first upgrade to Rails 3 in case you haven't and make sure your application still runs as expected before attempting to update to Rails 3.1. Then take heed of the following changes:

Rails 3.1 requires at least Ruby 1.8.7

Rails 3.1 requires Ruby 1.8.7 or higher. Support for all of the previous Ruby versions has been dropped officially and you should upgrade as early as possible. Rails 3.1 is also compatible with Ruby 1.9.2.

TIP: Note that Ruby 1.8.7 p248 and p249 have marshalling bugs that crash Rails. Ruby Enterprise Edition have these fixed since release 1.8.7-2010.02 though. On the 1.9 front, Ruby 1.9.1 is not usable because it outright segfaults, so if you want to use 1.9.x jump on 1.9.2 for smooth sailing.

What to update in your apps

The following changes are meant for upgrading your application to Rails 3.1.3, the latest 3.1.x version of Rails.

Gemfile

Make the following changes to your Gemfile.

gem 'rails', '= 3.1.3'
gem 'mysql2'

# Needed for the new asset pipeline
group :assets do
  gem 'sass-rails',   "~> 3.1.5"
  gem 'coffee-rails', "~> 3.1.1"
  gem 'uglifier',     ">= 1.0.3"
end

# jQuery is the default JavaScript library in Rails 3.1
gem 'jquery-rails'

config/application.rb

config/environments/development.rb

config/environments/production.rb

config/environments/test.rb

# Configure static asset server for tests with Cache-Control for performance
config.serve_static_assets = true
config.static_cache_control = "public, max-age=3600"

config/initializers/wrap_parameters.rb

Remove :cache and :concat options in asset helpers references in views

Creating a Rails 3.1 application

# You should have the 'rails' RubyGem installed
$ rails new myapp
$ cd myapp

Vendoring Gems

Rails now uses a Gemfile in the application root to determine the gems you require for your application to start. This Gemfile is processed by the Bundler gem, which then installs all your dependencies. It can even install all the dependencies locally to your application so that it doesn't depend on the system gems.

More information: - bundler homepage

Living on the Edge

Bundler and Gemfile makes freezing your Rails application easy as pie with the new dedicated bundle command. If you want to bundle straight from the Git repository, you can pass the --edge flag:

$ rails new myapp --edge

If you have a local checkout of the Rails repository and want to generate an application using that, you can pass the --dev flag:

$ ruby /path/to/rails/railties/bin/rails new myapp --dev

Rails Architectural Changes

Assets Pipeline

The major change in Rails 3.1 is the Assets Pipeline. It makes CSS and JavaScript first-class code citizens and enables proper organization, including use in plugins and engines.

The assets pipeline is powered by Sprockets and is covered in the Asset Pipeline guide.

HTTP Streaming

HTTP Streaming is another change that is new in Rails 3.1. This lets the browser download your stylesheets and JavaScript files while the server is still generating the response. This requires Ruby 1.9.2, is opt-in and requires support from the web server as well, but the popular combo of NGINX and Unicorn is ready to take advantage of it.

Default JS library is now jQuery

jQuery is the default JavaScript library that ships with Rails 3.1. But if you use Prototype, it's simple to switch.

$ rails new myapp -j prototype

Identity Map

Active Record has an Identity Map in Rails 3.1. An identity map keeps previously instantiated records and returns the object associated with the record if accessed again. The identity map is created on a per-request basis and is flushed at request completion.

Rails 3.1 comes with the identity map turned off by default.

Railties

Action Pack

Action Controller

Action Dispatch

Action View

Keys are dasherized. Values are JSON-encoded, except for strings and symbols.

Active Record

Active Model

Active Resource

Active Support

Deprecations:

Credits

See the full list of contributors to Rails for the many people who spent many hours making Rails, the stable and robust framework it is. Kudos to all of them.

Rails 3.1 Release Notes were compiled by Vijay Dev