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Ruby on Rails 4.0 Release Notes
Highlights in Rails 4.0:
- Ruby 1.9.3 only
- Strong Parameters
- Turbolinks
- Russian Doll Caching
- Asynchronous Mailers
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
TODO. Give a list and then talk about each of them briefly. We can point to relevant code commits or documentation from these sections.
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)
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/
dir. Runrake update:bin
to getbin/bundle
,bin/rails
, andbin/rake
. -
Threadsafe on by default
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 AP 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!
.
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, use Module#local_constants instead (which returns symbols).
-
BufferedLogger is deprecated. Use ActiveSupport::Logger, or the logger from Ruby stdlib.
-
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 some metadata columns to
schema_migrations
table.migrated_at
fingerprint
- an md5 hash of the migration.name
- the filename minus version and extension.
-
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.
-
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 usingwhere(...)
.find_last_by_...
can be rewritten usingwhere(...).last
.scoped_by_...
can be rewritten usingwhere(...)
.find_or_initialize_by_...
can be rewritten usingwhere(...).first_or_initialize
.find_or_create_by_...
can be rewritten usingfind_or_create_by(...)
orwhere(...).first_or_create
.find_or_create_by_...!
can be rewritten usingfind_or_create_by!(...)
orwhere(...).first_or_create!
.
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.