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Ruby on Rails 4.0 Release Notes
Highlights in Rails 4.0:
- Ruby 2.0 preferred; 1.9.3+ required
- Strong Parameters
- Turbolinks
- Russian Doll Caching
These release notes cover only the major changes. To know about various bug fixes and changes, please refer to the change logs or check out the list of commits in the main Rails repository on GitHub.
Upgrading to Rails 4.0
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 3.2 in case you haven't and make sure your application still runs as expected before attempting an update to Rails 4.0. A list of things to watch out for when upgrading is available in the Upgrading to Rails guide.
Creating a Rails 4.0 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
Major Features
Upgrade
- Ruby 1.9.3 (commit) - Ruby 2.0 preferred; 1.9.3+ required
- New deprecation policy - Deprecated features are warnings in Rails 4.0 and will be removed in Rails 4.1.
- ActionPack page and action caching (commit) - Page and action caching are extracted to a separate gem. Page and action caching requires too much manual intervention (manually expiring caches when the underlying model objects are updated). Instead, use Russian doll caching.
- ActiveRecord observers (commit) - Observers are extracted to a separate gem. Observers are only needed for page and action caching, and can lead to spaghetti code.
- ActiveRecord session store (commit) - The ActiveRecord session store is extracted to a separate gem. Storing sessions in SQL is costly. Instead, use cookie sessions, memcache sessions, or a custom session store.
- ActiveModel mass assignment protection (commit) - Rails 3 mass assignment protection is deprecated. Instead, use strong parameters.
- ActiveResource (commit) - ActiveResource is extracted to a separate gem. ActiveResource was not widely used.
- vendor/plugins removed (commit) - Use a Gemfile to manage installed gems.
ActionPack
- Strong parameters (commit) - Only allow whitelisted parameters to update model objects (
params.permit(:title, :text)
). - Routing concerns (commit) - In the routing DSL, factor out common subroutes (
comments
from/posts/1/comments
and/videos/1/comments
). - ActionController::Live (commit) - Stream JSON with
response.stream
. - Declarative ETags (commit) - Add controller-level etag additions that will be part of the action etag computation
- Russian doll caching (commit) - Cache nested fragments of views. Each fragment expires based on a set of dependencies (a cache key). The cache key is usually a template version number and a model object.
- Turbolinks (commit) - Serve only one initial HTML page. When the user navigates to another page, use pushState to update the URL and use AJAX to update the title and body.
- Decouple ActionView from ActionController (commit) - ActionView was decoupled from ActionPack and will be moved to a separated gem in Rails 4.1.
- Do not depend on ActiveModel (commit) - ActionPack no longer depends on ActiveModel.
General
- ActiveModel::Model (commit) -
ActiveModel::Model
, a mixin to make normal Ruby objects to work with ActionPack out of box (ex. forform_for
) - New scope API (commit) - Scopes must always use callables.
- Schema cache dump (commit) - To improve Rails boot time, instead of loading the schema directly from the database, load the schema from a dump file.
- Support for specifying transaction isolation level (commit) - Choose whether repeatable reads or improved performance (less locking) is more important.
- Dalli (commit) - Use Dalli memcache client for the memcache store.
- Notifications start & finish (commit) - Active Support instrumentation reports start and finish notifications to subscribers.
- Thread safe by default (commit) - Rails can run in threaded app servers without additional configuration. Note: Check that the gems you are using are threadsafe.
- PATCH verb (commit) - In Rails, PATCH replaces PUT. PATCH is used for partial updates of resources.
Security
- match do not catch all (commit) - In the routing DSL, match requires the HTTP verb or verbs to be specified.
- html entities escaped by default (commit) - Strings rendered in erb are escaped unless wrapped with
raw
orhtml_safe
is called. - New security headers (commit) - Rails sends the following headers with every HTTP request:
X-Frame-Options
(prevents clickjacking by forbidding the browser from embedding the page in a frame),X-XSS-Protection
(asks the browser to halt script injection) andX-Content-Type-Options
(prevents the browser from opening a jpeg as an exe).
Extraction of features to gems
In Rails 4.0, several features have been extracted into gems. You can simply add the extracted gems to your Gemfile
to bring the functionality back.
- Hash-based & Dynamic finder methods (GitHub)
- Mass assignment protection in Active Record models (GitHub, Pull Request)
- ActiveRecord::SessionStore (GitHub, Pull Request)
- Active Record Observers (GitHub, Commit)
- Active Resource (GitHub, Pull Request, Blog)
- Action Caching (GitHub, Pull Request)
- Page Caching (GitHub, Pull Request)
- Sprockets (GitHub)
- Performance tests (GitHub, Pull Request)
Documentation
-
Guides are rewritten in GitHub Flavored Markdown.
-
Guides have a responsive design.
Railties
Please refer to the Changelog for detailed changes.
Notable changes
-
New test locations
test/models
,test/helpers
,test/controllers
, andtest/mailers
. Corresponding rake tasks added as well. (Pull Request) -
Your app's executables now live in the
bin/
directory. Runrake rails:update:bin
to getbin/bundle
,bin/rails
, andbin/rake
. -
Threadsafe on by default
-
Ability to use a custom builder by passing
--builder
(or-b
) torails new
has been removed. Consider using application templates instead. (Pull Request)
Deprecations
-
config.threadsafe!
is deprecated in favor ofconfig.eager_load
which provides a more fine grained control on what is eager loaded. -
Rails::Plugin
has gone. Instead of adding plugins tovendor/plugins
use gems or bundler with path or git dependencies.
Action Mailer
Please refer to the Changelog for detailed changes.
Notable changes
Deprecations
Active Model
Please refer to the Changelog for detailed changes.
Notable changes
-
Add
ActiveModel::ForbiddenAttributesProtection
, a simple module to protect attributes from mass assignment when non-permitted attributes are passed. -
Added
ActiveModel::Model
, a mixin to make Ruby objects work with Action Pack out of box.
Deprecations
Active Support
Please refer to the Changelog for detailed changes.
Notable changes
-
Replace deprecated
memcache-client
gem withdalli
in ActiveSupport::Cache::MemCacheStore. -
Optimize ActiveSupport::Cache::Entry to reduce memory and processing overhead.
-
Inflections can now be defined per locale.
singularize
andpluralize
accept locale as an extra argument. -
Object#try
will now return nil instead of raise a NoMethodError if the receiving object does not implement the method, but you can still get the old behavior by using the newObject#try!
. -
String#to_date
now raisesArgument Error: invalid date
instead ofNoMethodError: undefined method 'div' for nil:NilClass
when given an invalid date. It is now the same asDate.parse
, and it accepts more invalid dates than 3.x, such as:# ActiveSupport 3.x "asdf".to_date # => NoMethodError: undefined method `div' for nil:NilClass "333".to_date # => NoMethodError: undefined method `div' for nil:NilClass # ActiveSupport 4 "asdf".to_date # => ArgumentError: invalid date "333".to_date # => Fri, 29 Nov 2013
Deprecations
-
Deprecate
ActiveSupport::TestCase#pending
method, useskip
from MiniTest instead. -
ActiveSupport::Benchmarkable#silence
has been deprecated due to its lack of thread safety. It will be removed without replacement in Rails 4.1. -
ActiveSupport::JSON::Variable
is deprecated. Define your own#as_json
and#encode_json
methods for custom JSON string literals. -
Deprecates the compatibility method
Module#local_constant_names
, useModule#local_constants
instead (which returns symbols). -
BufferedLogger
is deprecated. UseActiveSupport::Logger
, or the logger from Ruby standard library. -
Deprecate
assert_present
andassert_blank
in favor ofassert object.blank?
andassert object.present?
Action Pack
Please refer to the Changelog for detailed changes.
Notable changes
- Change the stylesheet of exception pages for development mode. Additionally display also the line of code and fragment that raised the exception in all exceptions pages.
Deprecations
Active Record
Please refer to the Changelog for detailed changes.
Notable changes
-
Improve ways to write
change
migrations, making the oldup
&down
methods no longer necessary.-
The methods
drop_table
andremove_column
are now reversible, as long as the necessary information is given. The methodremove_column
used to accept multiple column names; instead useremove_columns
(which is not revertible). The methodchange_table
is also reversible, as long as its block doesn't callremove
,change
orchange_default
-
New method
reversible
makes it possible to specify code to be run when migrating up or down. See the Guide on Migration -
New method
revert
will revert a whole migration or the given block. If migrating down, the given migration / block is run normally. See the Guide on Migration
-
-
Adds PostgreSQL array type support. Any datatype can be used to create an array column, with full migration and schema dumper support.
-
Add
Relation#load
to explicitly load the record and returnself
. -
Model.all
now returns anActiveRecord::Relation
, rather than an array of records. UseRelation#to_a
if you really want an array. In some specific cases, this may cause breakage when upgrading. -
Added
ActiveRecord::Migration.check_pending!
that raises an error if migrations are pending. -
Added custom coders support for
ActiveRecord::Store
. Now you can set your custom coder like this:store :settings, accessors: [ :color, :homepage ], coder: JSON
-
mysql
andmysql2
connections will setSQL_MODE=STRICT_ALL_TABLES
by default to avoid silent data loss. This can be disabled by specifyingstrict: false
in yourdatabase.yml
. -
Remove IdentityMap.
-
Remove automatic execution of EXPLAIN queries. The option
active_record.auto_explain_threshold_in_seconds
is no longer used and should be removed. -
Adds
ActiveRecord::NullRelation
andActiveRecord::Relation#none
implementing the null object pattern for the Relation class. -
Added
create_join_table
migration helper to create HABTM join tables. -
Allows PostgreSQL hstore records to be created.
Deprecations
-
Deprecated the old-style hash based finder API. This means that methods which previously accepted "finder options" no longer do.
-
All dynamic methods except for
find_by_...
andfind_by_...!
are deprecated. Here's how you can rewrite the code:* `find_all_by_...` can be rewritten using `where(...)`. * `find_last_by_...` can be rewritten using `where(...).last`. * `scoped_by_...` can be rewritten using `where(...)`. * `find_or_initialize_by_...` can be rewritten using `find_or_initialize_by(...)`. * `find_or_create_by_...` can be rewritten using `find_or_create_by(...)`. * `find_or_create_by_...!` can be rewritten using `find_or_create_by!(...)`.
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.