Rails 3.0 is ponies and rainbows! It's going to cook you dinner and fold your laundry. You're going to wonder how life was ever possible before it arrived. It's the Best Version of Rails We've Ever Done!
But seriously now, it's really good stuff. There are all the good ideas brought over from when the Merb team joined the party and brought a focus on framework agnosticism, slimmer and faster internals, and a handful of tasty APIs. If you're coming to Rails 3.0 from Merb 1.x, you should recognize lots. If you're coming from Rails 2.x, you're going to love it too.
Even if you don't give a hoot about any of our internal cleanups, Rails 3.0 is going to delight. We have a bunch of new features and improved APIs. It's never been a better time to be a Rails developer. Some of the highlights are:
On top of all that, we've tried our best to deprecate the old APIs with nice warnings. That means that you can move your existing application to Rails 3 without immediately rewriting all your old code to the latest best practices.
These release notes cover the major upgrades, but don't include every little bug fix and change. Rails 3.0 consists of almost 4,000 commits by more than 250 authors! If you want to see everything, check out the list of commits in the main Rails repository on GitHub.
ChaptersTo install Rails 3:
# Use sudo if your setup requires it $ gem install rails
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 2.3.5 and make sure your application still runs as expected before attempting to update to Rails 3. Then take heed of the following changes:
Rails 3.0 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 3.0 is also compatible with Ruby 1.9.2.
Note that Ruby 1.8.7 p248 and p249 have marshalling bugs that crash Rails 3.0. 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 on Rails 3.0, so if you want to use Rails 3 with 1.9.x jump on 1.9.2 for smooth sailing.
As part of the groundwork for supporting running multiple Rails applications in the same process, Rails 3 introduces the concept of an Application object. An application object holds all the application specific configurations and is very similar in nature to config/environment.rb from the previous versions of Rails.
Each Rails application now must have a corresponding application object. The application object is defined in config/application.rb. If you're upgrading an existing application to Rails 3, you must add this file and move the appropriate configurations from config/environment.rb to config/application.rb.
The new script/rails replaces all the scripts that used to be in the script directory. You do not run script/rails directly though, the rails command detects it is being invoked in the root of a Rails application and runs the script for you. Intended usage is:
$ rails console # instead of script/console $ rails g scaffold post title:string # instead of script/generate scaffold post title:string
Run rails --help for a list of all the options.
The config.gem method is gone and has been replaced by using bundler and a Gemfile, see Vendoring Gems below.
To help with the upgrade process, a plugin named Rails Upgrade has been created to automate part of it.
Simply install the plugin, then run rake rails:upgrade:check to check your app for pieces that need to be updated (with links to information on how to update them). It also offers a task to generate a Gemfile based on your current config.gem calls and a task to generate a new routes file from your current one. To get the plugin, simply run the following:
$ ruby script/plugin install git://github.com/rails/rails_upgrade.git
You can see an example of how that works at Rails Upgrade is now an Official Plugin
Aside from Rails Upgrade tool, if you need more help, there are people on IRC and rubyonrails-talk that are probably doing the same thing, possibly hitting the same issues. Be sure to blog your own experiences when upgrading so others can benefit from your knowledge!
# You should have the 'rails' RubyGem installed $ rails new myapp $ cd myapp
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 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
Bundler and Gemfile makes freezing your Rails application easy as pie with the new dedicated bundle command, so rake freeze is no longer relevant and has been dropped.
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/bin/rails new myapp --dev
There are six major changes in the architecture of Rails.
Railties was updated to provide a consistent plugin API for the entire Rails framework as well as a total rewrite of generators and the Rails bindings, the result is that developers can now hook into any significant stage of the generators and application framework in a consistent, defined manner.
With the merge of Merb and Rails, one of the big jobs was to remove the tight coupling between Rails core components. This has now been achieved, and all Rails core components are now using the same API that you can use for developing plugins. This means any plugin you make, or any core component replacement (like DataMapper or Sequel) can access all the functionality that the Rails core components have access to and extend and enhance at will.
More information: - The Great Decoupling
Part of decoupling the core components was extracting all ties to Active Record from Action Pack. This has now been completed. All new ORM plugins now just need to implement Active Model interfaces to work seamlessly with Action Pack.
More information: - Make Any Ruby Object Feel Like ActiveRecord
Another big part of decoupling the core components was creating a base superclass that is separated from the notions of HTTP in order to handle rendering of views etc. This creation of AbstractController allowed ActionController and ActionMailer to be greatly simplified with common code removed from all these libraries and put into Abstract Controller.
More Information: - Rails Edge Architecture
Arel (or Active Relation) has been taken on as the underpinnings of Active Record and is now required for Rails. Arel provides an SQL abstraction that simplifies out Active Record and provides the underpinnings for the relation functionality in Active Record.
More information: - Why I wrote Arel
Action Mailer ever since its beginnings has had monkey patches, pre parsers and even delivery and receiver agents, all in addition to having TMail vendored in the source tree. Version 3 changes that with all email message related functionality abstracted out to the Mail gem. This again reduces code duplication and helps create definable boundaries between Action Mailer and the email parser.
More information: - New Action Mailer API in Rails 3
The documentation in the Rails tree is being updated with all the API changes, additionally, the Rails Edge Guides are being updated one by one to reflect the changes in Rails 3.0. The guides at guides.rubyonrails.org however will continue to contain only the stable version of Rails (at this point, version 2.3.5, until 3.0 is released).
More Information: - Rails Documentation Projects
A large amount of work has been done with I18n support in Rails 3, including the latest I18n gem supplying many speed improvements.
ActiveModel::Translation and ActiveModel::Validations. There is also an errors.messages fallback for translations.More Information: - Rails 3 I18n changes
With the decoupling of the main Rails frameworks, Railties got a huge overhaul so as to make linking up frameworks, engines, or plugins as painless and extensible as possible:
YourAppName.boot for example, makes interacting with other applications a lot easier.Rails.root/app is now added to the load path, so you can make app/observers/user_observer.rb and Rails will load it without any modifications.Rails 3.0 now provides a Rails.config object, which provides a central repository of all sorts of Rails wide configuration options.
Application generation has received extra flags allowing you to skip the installation of test-unit, Active Record, Prototype and Git. Also a new --dev flag has been added which sets the application up with the Gemfile pointing to your Rails checkout (which is determined by the path to the rails binary). See rails --help for more info.
Railties generators got a huge amount of attention in Rails 3.0, basically:
rails generate foo will look for generators/foo_generator.Rails.root/lib/templates.Rails::Generators::TestCase is also supplied so you can create your own generators and test them.Also, the views generated by Railties generators had some overhaul:
div tags instead of p tags._form partials, instead of duplicated code in the edit and new views.f.submit which returns "Create ModelName" or "Update ModelName" depending on the state of the object passed in.Finally a couple of enhancements were added to the rake tasks:
rake db:forward was added, allowing you to roll forward your migrations individually or in groups.rake routes CONTROLLER=x was added allowing you to just view the routes for one controller.Railties now deprecates:
RAILS_ROOT in favor of Rails.root,RAILS_ENV in favor of Rails.env, andRAILS_DEFAULT_LOGGER in favor of Rails.logger.PLUGIN/rails/tasks, and PLUGIN/tasks are no longer loaded all tasks now must be in PLUGIN/lib/tasks.
More information:
There have been significant internal and external changes in Action Pack.
Abstract Controller pulls out the generic parts of Action Controller into a reusable module that any library can use to render templates, render partials, helpers, translations, logging, any part of the request response cycle. This abstraction allowed ActionMailer::Base to now just inherit from AbstractController and just wrap the Rails DSL onto the Mail gem.
It also provided an opportunity to clean up Action Controller, abstracting out what could to simplify the code.
Note however that Abstract Controller is not a user facing API, you will not run into it in your day to day use of Rails.
More Information: - Rails Edge Architecture
application_controller.rb now has protect_from_forgery on by default.cookie_verifier_secret has been deprecated and now instead it is assigned through Rails.application.config.cookie_secret and moved into its own file: config/initializers/cookie_verification_secret.rb.session_store was configured in ActionController::Base.session, and that is now moved to Rails.application.config.session_store. Defaults are set up in config/initializers/session_store.rb.cookies.secure allowing you to set encrypted values in cookies with cookie.secure[:key] => value.cookies.permanent allowing you to set permanent values in the cookie hash cookie.permanent[:key] => value that raise exceptions on signed values if verification failures.:notice => 'This is a flash message' or :alert => 'Something went wrong' to the format call inside a respond_to block. The flash[] hash still works as previously.respond_with method has now been added to your controllers simplifying the venerable format blocks.ActionController::Responder added allowing you flexibility in how your responses get generated.Deprecations:
filter_parameter_logging is deprecated in favor of config.filter_parameters << :password.More Information:
Action Dispatch is new in Rails 3.0 and provides a new, cleaner implementation for routing.
rack_mount with a Rails DSL on top, it is a stand alone piece of software.Routes defined by each application are now name spaced within your Application module, that is:
# Instead of: ActionController::Routing::Routes.draw do |map| map.resources :posts end # You do: AppName::Application.routes do resources :posts end
Added match method to the router, you can also pass any Rack application to the matched route.
Added constraints method to the router, allowing you to guard routers with defined constraints.
Added scope method to the router, allowing you to namespace routes for different languages or different actions, for example:
scope 'es' do
resources :projects, :path_names => { :edit => 'cambiar' }, :path => 'proyecto'
end
# Gives you the edit action with /es/proyecto/1/cambiar
Added root method to the router as a short cut for match '/', :to => path.
You can pass optional segments into the match, for example match "/:controller(/:action(/:id))(.:format)", each parenthesized segment is optional.
Routes can be expressed via blocks, for example you can call controller :home { match '/:action' }.
The old style map commands still work as before with a backwards compatibility layer, however this will be removed in the 3.1 release.
Deprecations
/:controller/:action/:id) is now commented out.:path_prefix no longer exists and :name_prefix now automatically adds "_" at the end of the given value.More Information: * The Rails 3 Router: Rack it Up * Revamped Routes in Rails 3 * Generic Actions in Rails 3
Major re-write was done in the Action View helpers, implementing Unobtrusive JavaScript (UJS) hooks and removing the old inline AJAX commands. This enables Rails to use any compliant UJS driver to implement the UJS hooks in the helpers.
What this means is that all previous remote_<method> helpers have been removed from Rails core and put into the Prototype Legacy Helper. To get UJS hooks into your HTML, you now pass :remote => true instead. For example:
form_for @post, :remote => true
Produces:
<form action="http://host.com" id="create-post" method="post" data-remote="true">
Helpers like form_for or div_for that insert content from a block use <%= now:
<%= form_for @post do |f| %> ... <% end %>
Your own helpers of that kind are expected to return a string, rather than appending to the output buffer by hand.
Helpers that do something else, like cache or content_for, are not affected by this change, they need <% as before.
h(string) to escape HTML output, it is on by default in all view templates. If you want the unescaped string, call raw(string).f.label :name will pull the :name translation.grouped_collection_select helper to Action View.content_for? has been added allowing you to check for the existence of content in a view before rendering.:value => nil to form helpers will set the field's value attribute to nil as opposed to using the default value:id => nil to form helpers will cause those fields to be rendered with no id attribute:alt => nil to image_tag will cause the img tag to render with no alt attributeActive Model is new in Rails 3.0. It provides an abstraction layer for any ORM libraries to use to interact with Rails by implementing an Active Model interface.
Part of decoupling the core components was extracting all ties to Active Record from Action Pack. This has now been completed. All new ORM plugins now just need to implement Active Model interfaces to work seamlessly with Action Pack.
More Information: - Make Any Ruby Object Feel Like ActiveRecord
Validations have been moved from Active Record into Active Model, providing an interface to validations that works across ORM libraries in Rails 3.
validates :attribute, options_hash shortcut method that allows you to pass options for all the validates class methods, you can pass more than one option to a validate method.validates method has the following options:
:acceptance => Boolean.:confirmation => Boolean.:exclusion => { :in => Enumerable }.:inclusion => { :in => Enumerable }.:format => { :with => Regexp, :on => :create }.:length => { :maximum => Fixnum }.:numericality => Boolean.:presence => Boolean.:uniqueness => Boolean.All the Rails version 2.3 style validation methods are still supported in Rails 3.0, the new validates method is designed as an additional aid in your model validations, not a replacement for the existing API.
You can also pass in a validator object, which you can then reuse between objects that use Active Model:
class TitleValidator < ActiveModel::EachValidator
Titles = ['Mr.', 'Mrs.', 'Dr.']
def validate_each(record, attribute, value)
unless Titles.include?(value)
record.errors[attribute] << 'must be a valid title'
end
end
end
class Person include ActiveModel::Validations attr_accessor :title validates :title, :presence => true, :title => true end # Or for Active Record class Person < ActiveRecord::Base validates :title, :presence => true, :title => true end
There's also support for introspection:
User.validators User.validators_on(:login)
More Information:
Active Record received a lot of attention in Rails 3.0, including abstraction into Active Model, a full update to the Query interface using Arel, validation updates, and many enhancements and fixes. All of the Rails 2.x API will be usable through a compatibility layer that will be supported until version 3.1.
Active Record, through the use of Arel, now returns relations on its core methods. The existing API in Rails 2.3.x is still supported and will not be deprecated until Rails 3.1 and not removed until Rails 3.2, however, the new API provides the following new methods that all return relations allowing them to be chained together:
where - provides conditions on the relation, what gets returned.select - choose what attributes of the models you wish to have returned from the database.group - groups the relation on the attribute supplied.having - provides an expression limiting group relations (GROUP BY constraint).joins - joins the relation to another table.clause - provides an expression limiting join relations (JOIN constraint).includes - includes other relations pre-loaded.order - orders the relation based on the expression supplied.limit - limits the relation to the number of records specified.lock - locks the records returned from the table.readonly - returns an read only copy of the data.from - provides a way to select relationships from more than one table.scope - (previously named_scope) return relations and can be chained together with the other relation methods.with_scope - and with_exclusive_scope now also return relations and so can be chained.default_scope - also works with relations.More Information:
:destroyed? to Active Record objects.:inverse_of to Active Record associations allowing you to pull the instance of an already loaded association without hitting the database.Additionally, many fixes in the Active Record branch:
TIME ZONE support fixed so it no longer inserts incorrect values.table_name is now cached.As well as the following deprecations:
named_scope in an Active Record class is deprecated and has been renamed to just scope.scope methods, you should move to using the relation methods, instead of a :conditions => {} finder method, for example scope :since, lambda {|time| where("created_at > ?", time) }.save(false) is deprecated, in favor of save(:validate => false).:en.errors.template.model.errors.on is deprecated in favor of model.errors[]
ActiveRecord::Base.colorize_logging and config.active_record.colorize_logging are deprecated in favor of Rails::LogSubscriber.colorize_logging or config.colorize_logging
While an implementation of State Machine has been in Active Record edge for some months now, it has been removed from the Rails 3.0 release.
Active Resource was also extracted out to Active Model allowing you to use Active Resource objects with Action Pack seamlessly.
first, last and all aliases for equivalent find scopes.find_every now does not return a ResourceNotFound error if nothing returned.save! which raises ResourceInvalid unless the object is valid?.update_attribute and update_attributes added to Active Resource models.exists?.SchemaDefinition to Schema and define_schema to schema.format of Active Resources rather than the content-type of remote errors to load errors.instance_eval for schema block.ActiveResource::ConnectionError#to_s when @response does not respond to #code or #message, handles Ruby 1.9 compatibility.load works with numeric arrays.Net::HTTP open_timeout.Deprecations:
save(false) is deprecated, in favor of save(:validate => false).URI.parse and .decode are deprecated and are no longer used in the library.A large effort was made in Active Support to make it cherry pickable, that is, you no longer have to require the entire Active Support library to get pieces of it. This allows the various core components of Rails to run slimmer.
These are the main changes in Active Support:
bundle install command.ActiveSupport::SafeBuffer.Array.uniq_by and Array.uniq_by!.Array#rand and backported Array#sample from Ruby 1.9.TimeZone.seconds_to_utc_offset returning wrong value.ActiveSupport::Notifications middleware.ActiveSupport.use_standard_json_time_format now defaults to true.ActiveSupport.escape_html_entities_in_json now defaults to false.Integer#multiple_of? accepts zero as an argument, returns false unless the receiver is zero.string.chars has been renamed to string.mb_chars.ActiveSupport::OrderedHash now can de-serialize through YAML.Object#presence that returns the object if it's #present? otherwise returns nil.String#exclude? core extension that returns the inverse of #include?.to_i to DateTime in ActiveSupport so to_yaml works correctly on models with DateTime attributes.Enumerable#exclude? to bring parity to Enumerable#include? and avoid if !x.include?.ActiveSupport::HashWithIndifferentAccess.Enumerable#sum now works will all enumerables, even if they don't respond to :size.inspect on a zero length duration returns '0 seconds' instead of empty string.element and collection to ModelName.String#to_time and String#to_datetime handle fractional seconds.:before and :after used in before and after callbacks.ActiveSupport::OrderedHash#to_a method returns an ordered set of arrays. Matches Ruby 1.9's Hash#to_a.MissingSourceFile exists as a constant but it is now just equal to LoadError.Class#class_attribute, to be able to declare a class-level attribute whose value is inheritable and overwritable by subclasses.DeprecatedCallbacks in ActiveRecord::Associations.Object#metaclass is now Kernel#singleton_class to match Ruby.The following methods have been removed because they are now available in Ruby 1.8.7 and 1.9.
Integer#even? and Integer#odd?
String#each_charString#start_with? and String#end_with? (3rd person aliases still kept)String#bytesizeObject#tapSymbol#to_procObject#instance_variable_defined?Enumerable#none?The security patch for REXML remains in Active Support because early patch-levels of Ruby 1.8.7 still need it. Active Support knows whether it has to apply it or not.
The following methods have been removed because they are no longer used in the framework:
Kernel#daemonizeObject#remove_subclasses_of Object#extend_with_included_modules_from, Object#extended_by
Class#remove_classRegexp#number_of_captures, Regexp.unoptionalize, Regexp.optionalize, Regexp#number_of_captures
Action Mailer has been given a new API with TMail being replaced out with the new Mail as the email library. Action Mailer itself has been given an almost complete re-write with pretty much every line of code touched. The result is that Action Mailer now simply inherits from Abstract Controller and wraps the Mail gem in a Rails DSL. This reduces the amount of code and duplication of other libraries in Action Mailer considerably.
app/mailers by default.attachments, headers and mail.attachments.inline method.Mail::Message objects, which can then be sent the deliver message to send itself.mail delivery method acts in a similar way to Action Controller's respond_to, and you can explicitly or implicitly render templates. Action Mailer will turn the email into a multipart email as needed.format.mime_type calls within the mail block and explicitly render specific types of text, or add layouts or different templates. The render call inside the proc is from Abstract Controller and supports the same options.Deprecations:
:charset, :content_type, :mime_version, :implicit_parts_order are all deprecated in favor of ActionMailer.default :key => value style declarations.create_method_name and deliver_method_name are deprecated, just call method_name which now returns a Mail::Message object.ActionMailer.deliver(message) is deprecated, just call message.deliver.template_root is deprecated, pass options to a render call inside a proc from the format.mime_type method inside the mail generation blockbody method to define instance variables is deprecated (body {:ivar => value}), just declare instance variables in the method directly and they will be available in the view.app/models is deprecated, use app/mailers instead.More Information:
See the full list of contributors to Rails for the many people who spent many hours making Rails 3. Kudos to all of them.
Rails 3.0 Release Notes were compiled by Mikel Lindsaar.