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Ruby on Rails 4.2 Release Notes
===============================
Highlights in Rails 4.2:
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](https://github.com/rails/rails/commits/master) in the main
Rails repository on GitHub.
--------------------------------------------------------------------------------
Upgrading to Rails 4.2
----------------------
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 4.1 in case you
haven't and make sure your application still runs as expected before attempting
an update to Rails 4.2. A list of things to watch out for when upgrading is
available in the
[Upgrading Ruby on Rails](upgrading_ruby_on_rails.html#upgrading-from-rails-4-1-to-rails-4-2)
guide.
Major Features
--------------
Railties
--------
Please refer to the
[Changelog](https://github.com/rails/rails/blob/4-2-stable/railties/CHANGELOG.md)
for detailed changes.
### Removals
* The `rails application` command has been removed without replacement.
([Pull Request](https://github.com/rails/rails/pull/11616))
### Notable changes
* Introduced `bin/setup` script to bootstrap an application.
([Pull Request](https://github.com/rails/rails/pull/15189))
* Changed default value for `config.assets.digest` to `true` in development.
([Pull Request](https://github.com/rails/rails/pull/15155))
* Introduced an API to register new extensions for `rake notes`.
([Pull Request](https://github.com/rails/rails/pull/14379))
* Introduced `Rails.gem_version` as a convenience method to return `Gem::Version.new(Rails.version)`.
([Pull Request](https://github.com/rails/rails/pull/14101))
Action Pack
-----------
Please refer to the
[Changelog](https://github.com/rails/rails/blob/4-2-stable/actionpack/CHANGELOG.md)
for detailed changes.
### Deprecations
* Deprecated support for setting the `to:` option of a router to a symbol or a
string that does not contain a `#` character:
get '/posts', to: MyRackApp => (No change necessary)
get '/posts', to: 'post#index' => (No change necessary)
get '/posts', to: 'posts' => get '/posts', controller: :posts
get '/posts', to: :index => get '/posts', action: :index
([Commit](https://github.com/rails/rails/commit/cc26b6b7bccf0eea2e2c1a9ebdcc9d30ca7390d9))
### Notable changes
* The `*_filter` family methods has been removed from the documentation. Their
usage are discouraged in favor of the `*_action` family methods:
after_filter => after_action
append_after_filter => append_after_action
append_around_filter => append_around_action
append_before_filter => append_before_action
around_filter => around_action
before_filter => before_action
prepend_after_filter => prepend_after_action
prepend_around_filter => prepend_around_action
prepend_before_filter => prepend_before_action
skip_after_filter => skip_after_action
skip_around_filter => skip_around_action
skip_before_filter => skip_before_action
skip_filter => skip_action_callback
If your application is depending on these methods, you should use the
replacement `*_action` methods instead. These methods will be deprecated in
the future and eventually removed from Rails.
(Commit [1](https://github.com/rails/rails/commit/6c5f43bab8206747a8591435b2aa0ff7051ad3de),
[2](https://github.com/rails/rails/commit/489a8f2a44dc9cea09154ee1ee2557d1f037c7d4))
* Added HTTP method `MKCALENDAR` from RFC-4791
([Pull Request](https://github.com/rails/rails/pull/15121))
* `*_fragment.action_controller` notifications now include the controller and action name
in the payload.
([Pull Request](https://github.com/rails/rails/pull/14137))
* Segments that are passed into URL helpers are now automatically escaped.
([Commit](https://github.com/rails/rails/commit/5460591f0226a9d248b7b4f89186bd5553e7768f))
* Improved Routing Error page with fuzzy matching for route search.
([Pull Request](https://github.com/rails/rails/pull/14619))
* Added option to disable logging of CSRF failures.
([Pull Request](https://github.com/rails/rails/pull/14280))
Action Mailer
-------------
Please refer to the
[Changelog](https://github.com/rails/rails/blob/4-2-stable/actionmailer/CHANGELOG.md)
for detailed changes.
### Notable changes
Active Record
-------------
Please refer to the
[Changelog](https://github.com/rails/rails/blob/4-2-stable/activerecord/CHANGELOG.md)
for detailed changes.
### Deprecations
* Deprecated using `.joins`, `.preload` and `.eager_load` with associations that
depends on the instance state (i.e. those defined with a scope that takes an
argument) without replacement.
([Commit](https://github.com/rails/rails/commit/ed56e596a0467390011bc9d56d462539776adac1))
* Deprecated passing Active Record objects to `.find` or `.exists?`. Call `#id`
on the objects first.
(Commit [1](https://github.com/rails/rails/commit/d92ae6ccca3bcfd73546d612efaea011270bd270),
[2](https://github.com/rails/rails/commit/d35f0033c7dec2b8d8b52058fb8db495d49596f7))
* Deprecated half-baked support for PostgreSQL range values with excluding
beginnings. We currently map PostgreSQL ranges to Ruby ranges. This conversion
is not fully possible because the Ruby range does not support excluded
beginnings.
The current solution of incrementing the beginning is not correct and is now
deprecated. For subtypes where we don't know how to increment (e.g. `#succ`
is not defined) it will raise an `ArgumentError` for ranges with excluding
beginnings.
([Commit](https://github.com/rails/rails/commit/91949e48cf41af9f3e4ffba3e5eecf9b0a08bfc3))
### Notable changes
* Added support for `#pretty_print` in `ActiveRecord::Base` objects.
([Pull Request](https://github.com/rails/rails/pull/15172))
* PostgreSQL and SQLite adapters no longer add a default limit of 255 characters
on string columns.
([Pull Request](https://github.com/rails/rails/pull/14579))
* `sqlite3:///some/path` now resolves to the absolute system path `/some/path`.
For relative paths, use `sqlite3:some/path` instead. (Previously, `sqlite3:///some/path`
resolved to the relative path `some/path`. This behaviour was deprecated on
Rails 4.1.)
([Pull Request](https://github.com/rails/rails/pull/14569))
* Introduced `#validate` as an alias for `#valid?`.
([Pull Request](https://github.com/rails/rails/pull/14456))
* `#touch` now accepts multiple attributes to be touched at once.
([Pull Request](https://github.com/rails/rails/pull/14423))
* Added support for fractional seconds for MySQL 5.6 and above.
(Pull Request [1](https://github.com/rails/rails/pull/8240), [2](https://github.com/rails/rails/pull/14359))
* Added support for the `citext` column type in PostgreSQL adapter.
([Pull Request](https://github.com/rails/rails/pull/12523))
* Added support for user-created range types in PostgreSQL adapter.
([Commit](https://github.com/rails/rails/commit/4cb47167e747e8f9dc12b0ddaf82bdb68c03e032))
Active Model
------------
Please refer to the
[Changelog](https://github.com/rails/rails/blob/4-2-stable/activemodel/CHANGELOG.md)
for detailed changes.
### Notable changes
* Introduced `#validate` as an alias for `#valid?`.
([Pull Request](https://github.com/rails/rails/pull/14456))
Active Support
--------------
Please refer to the
[Changelog](https://github.com/rails/rails/blob/4-2-stable/activesupport/CHANGELOG.md)
for detailed changes.
### Removals
* Removed deprecated `Numeric#ago`, `Numeric#until`, `Numeric#since`,
`Numeric#from_now`. ([Commit](https://github.com/rails/rails/commit/f1eddea1e3f6faf93581c43651348f48b2b7d8bb))
* Removed deprecated string based terminators for `ActiveSupport::Callbacks`.
([Pull Request](https://github.com/rails/rails/pull/15100))
### Deprecations
* Deprecated `Class#superclass_delegating_accessor`, use `Class#class_attribute`
instead. ([Pull Request](https://github.com/rails/rails/pull/14271))
* Deprecated `ActiveSupport::SafeBuffer#prepend!` as `ActiveSupport::SafeBuffer#prepend`
now performs the same function. ([Pull Request](https://github.com/rails/rails/pull/14529))
### Notable changes
* The `humanize` inflector helper now strips any leading underscores.
([Commit](https://github.com/rails/rails/commit/daaa21bc7d20f2e4ff451637423a25ff2d5e75c7))
* Added `SecureRandom::uuid_v3` and `SecureRandom::uuid_v5`.
([Pull Request](https://github.com/rails/rails/pull/12016))
* Introduce `Concern#class_methods` as an alternative to `module ClassMethods`,
as well as `Kernel#concern` to avoid the `module Foo; extend ActiveSupport::Concern; end`
boilerplate. ([Commit](https://github.com/rails/rails/commit/b16c36e688970df2f96f793a759365b248b582ad))
Credits
-------
See the
[full list of contributors to Rails](http://contributors.rubyonrails.org/) for
the many people who spent many hours making Rails, the stable and robust
framework it is. Kudos to all of them.
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