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<h2>A Guide for Upgrading Ruby on Rails</h2><p>This guide provides steps to be followed when you upgrade your applications to a newer version of Ruby on Rails. These steps are also available in individual release guides.</p>
<div id="subCol">
<h3 class="chapter"><img src="images/chapters_icon.gif" alt="" />Chapters</h3>
<ol class="chapters">
<li>
<a href="#general-advice">General Advice</a>
<ul>
<li><a href="#test-coverage">Test Coverage</a></li>
<li><a href="#ruby-versions">Ruby Versions</a></li>
<li><a href="#the-rake-task">The Rake Task</a></li>
</ul>
</li>
<li>
<a href="#upgrading-from-rails-4-1-to-rails-4-2">Upgrading from Rails 4.1 to Rails 4.2</a>
<ul>
<li><a href="#web-console">Web Console</a></li>
<li><a href="#responders">Responders</a></li>
<li><a href="#error-handling-in-transaction-callbacks">Error handling in transaction callbacks</a></li>
<li><a href="#ordering-of-test-cases">Ordering of test cases</a></li>
<li><a href="#serialized-attributes">Serialized attributes</a></li>
<li><a href="#after-bundle-in-rails-templates"><code>after_bundle</code> in Rails templates</a></li>
<li><a href="#rails-html-sanitizer">Rails Html Sanitizer</a></li>
<li><a href="#rails-dom-testing">Rails DOM Testing</a></li>
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<li><a href="#csrf-protection-from-remote-script-tags">CSRF protection from remote <code><script></code> tags</a></li>
<li><a href="#spring">Spring</a></li>
<li><a href="#config-secrets-yml"><code>config/secrets.yml</code></a></li>
<li><a href="#changes-to-test-helper">Changes to test helper</a></li>
<li><a href="#cookies-serializer">Cookies serializer</a></li>
<li><a href="#flash-structure-changes">Flash structure changes</a></li>
<li><a href="#changes-in-json-handling">Changes in JSON handling</a></li>
<li><a href="#usage-of-return-within-inline-callback-blocks">Usage of <code>return</code> within inline callback blocks</a></li>
<li><a href="#methods-defined-in-active-record-fixtures">Methods defined in Active Record fixtures</a></li>
<li><a href="#i18n-enforcing-available-locales">I18n enforcing available locales</a></li>
<li><a href="#mutator-methods-called-on-relation">Mutator methods called on Relation</a></li>
<li><a href="#changes-on-default-scopes">Changes on Default Scopes</a></li>
<li><a href="#rendering-content-from-string">Rendering content from string</a></li>
<li><a href="#postgresql-json-and-hstore-datatypes">PostgreSQL json and hstore datatypes</a></li>
<li><a href="#explicit-block-use-for-activesupport-callbacks">Explicit block use for <code>ActiveSupport::Callbacks</code></a></li>
</ul>
</li>
<li>
<a href="#upgrading-from-rails-3-2-to-rails-4-0">Upgrading from Rails 3.2 to Rails 4.0</a>
<ul>
<li><a href="#http-patch">HTTP PATCH</a></li>
<li><a href="#upgrading-from-rails-3-2-to-rails-4-0-gemfile">Gemfile</a></li>
<li><a href="#upgrading-from-rails-3-2-to-rails-4-0-vendor-plugins">vendor/plugins</a></li>
<li><a href="#upgrading-from-rails-3-2-to-rails-4-0-active-record">Active Record</a></li>
<li><a href="#active-resource">Active Resource</a></li>
<li><a href="#active-model">Active Model</a></li>
<li><a href="#action-pack">Action Pack</a></li>
<li><a href="#active-support">Active Support</a></li>
<li><a href="#helpers-loading-order">Helpers Loading Order</a></li>
<li><a href="#active-record-observer-and-action-controller-sweeper">Active Record Observer and Action Controller Sweeper</a></li>
<li><a href="#sprockets-rails">sprockets-rails</a></li>
<li><a href="#sass-rails">sass-rails</a></li>
</ul>
</li>
<li>
<a href="#upgrading-from-rails-3-1-to-rails-3-2">Upgrading from Rails 3.1 to Rails 3.2</a>
<ul>
<li><a href="#upgrading-from-rails-3-1-to-rails-3-2-gemfile">Gemfile</a></li>
<li><a href="#upgrading-from-rails-3-1-to-rails-3-2-config-environments-development-rb">config/environments/development.rb</a></li>
<li><a href="#upgrading-from-rails-3-1-to-rails-3-2-config-environments-test-rb">config/environments/test.rb</a></li>
<li><a href="#upgrading-from-rails-3-1-to-rails-3-2-vendor-plugins">vendor/plugins</a></li>
<li><a href="#upgrading-from-rails-3-1-to-rails-3-2-active-record">Active Record</a></li>
</ul>
</li>
<li>
<a href="#upgrading-from-rails-3-0-to-rails-3-1">Upgrading from Rails 3.0 to Rails 3.1</a>
<ul>
<li><a href="#gemfile">Gemfile</a></li>
<li><a href="#config-application-rb">config/application.rb</a></li>
<li><a href="#upgrading-from-rails-3-0-to-rails-3-1-config-environments-development-rb">config/environments/development.rb</a></li>
<li><a href="#config-environments-production-rb">config/environments/production.rb</a></li>
<li><a href="#upgrading-from-rails-3-0-to-rails-3-1-config-environments-test-rb">config/environments/test.rb</a></li>
<li><a href="#config-initializers-wrap-parameters-rb">config/initializers/wrap_parameters.rb</a></li>
<li><a href="#config-initializers-session-store-rb">config/initializers/session_store.rb</a></li>
<li><a href="#remove-cache-and-concat-options-in-asset-helpers-references-in-views">Remove :cache and :concat options in asset helpers references in views</a></li>
</ul>
</li>
</ol>
</div>
</div>
</div>
<div id="container">
<div class="wrapper">
<div id="mainCol">
<h3 id="general-advice">1 General Advice</h3><p>Before attempting to upgrade an existing application, you should be sure you have a good reason to upgrade. You need to balance several factors: the need for new features, the increasing difficulty of finding support for old code, and your available time and skills, to name a few.</p><h4 id="test-coverage">1.1 Test Coverage</h4><p>The best way to be sure that your application still works after upgrading is to have good test coverage before you start the process. If you don't have automated tests that exercise the bulk of your application, you'll need to spend time manually exercising all the parts that have changed. In the case of a Rails upgrade, that will mean every single piece of functionality in the application. Do yourself a favor and make sure your test coverage is good <em>before</em> you start an upgrade.</p><h4 id="ruby-versions">1.2 Ruby Versions</h4><p>Rails generally stays close to the latest released Ruby version when it's released:</p>
<ul>
<li>Rails 3 and above require Ruby 1.8.7 or higher. Support for all of the previous Ruby versions has been dropped officially. You should upgrade as early as possible.</li>
<li>Rails 3.2.x is the last branch to support Ruby 1.8.7.</li>
<li>Rails 4 prefers Ruby 2.0 and requires 1.9.3 or newer.</li>
</ul>
<div class="info"><p>Ruby 1.8.7 p248 and p249 have marshaling bugs that crash Rails. Ruby Enterprise Edition has these fixed since the release of 1.8.7-2010.02. 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 straight to 1.9.3 for smooth sailing.</p></div><h4 id="the-rake-task">1.3 The Rake Task</h4><p>Rails provides the <code>rails:update</code> rake task. After updating the Rails version
in the Gemfile, run this rake task.
This will help you with the creation of new files and changes of old files in an
interactive session.</p><div class="code_container">
<pre class="brush: plain; gutter: false; toolbar: false">
$ rake rails:update
identical config/boot.rb
exist config
conflict config/routes.rb
Overwrite /myapp/config/routes.rb? (enter "h" for help) [Ynaqdh]
force config/routes.rb
conflict config/application.rb
Overwrite /myapp/config/application.rb? (enter "h" for help) [Ynaqdh]
force config/application.rb
conflict config/environment.rb
...
</pre>
</div>
<p>Don't forget to review the difference, to see if there were any unexpected changes.</p><h3 id="upgrading-from-rails-4-1-to-rails-4-2">2 Upgrading from Rails 4.1 to Rails 4.2</h3><div class="note"><p>This section is a work in progress, please help to improve this by sending
a <a href="https://github.com/rails/rails/edit/master/guides/source/upgrading_ruby_on_rails.md">pull request</a>.</p></div><h4 id="web-console">2.1 Web Console</h4><p>First, add <code>gem 'web-console', '~> 2.0'</code> to the <code>:development</code> group in your Gemfile and run <code>bundle install</code> (it won't have been included when you upgraded Rails). Once it's been installed, you can simply drop a reference to the console helper (i.e., <code><%= console %></code>) into any view you want to enable it for. A console will also be provided on any error page you view in your development environment.</p><p>Additionally, you can tell Rails to automatically mount a VT100-compatible console on a predetermined path by setting the appropriate configuration flags in your development config:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
# config/environments/development.rb
config.web_console.automount = true
config.web_console.default_mount_path = '/terminal' # Optional, defaults to /console
</pre>
</div>
<h4 id="responders">2.2 Responders</h4><p><code>respond_with</code> and the class-level <code>respond_to</code> methods have been extracted to the <code>responders</code> gem. To use them, simply add <code>gem 'responders', '~> 2.0'</code> to your Gemfile. Calls to <code>respond_with</code> and <code>respond_to</code> (again, at the class level) will no longer work without having included the <code>responders</code> gem in your dependencies:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
# app/controllers/users_controller.rb
class UsersController < ApplicationController
respond_to :html, :json
def show
@user = User.find(params[:id])
respond_with @user
end
end
</pre>
</div>
<p>Instance-level <code>respond_to</code> is unaffected and does not require the additional gem:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
# app/controllers/users_controller.rb
class UsersController < ApplicationController
def show
@user = User.find(params[:id])
respond_to do |format|
format.html
format.json { render json: @user }
end
end
end
</pre>
</div>
<p>See <a href="https://github.com/rails/rails/pull/16526">#16526</a> for more details.</p><h4 id="error-handling-in-transaction-callbacks">2.3 Error handling in transaction callbacks</h4><p>Currently, Active Record suppresses errors raised
within <code>after_rollback</code> or <code>after_commit</code> callbacks and only prints them to
the logs. In the next version, these errors will no longer be suppressed.
Instead, the errors will propagate normally just like in other Active
Record callbacks.</p><p>When you define a <code>after_rollback</code> or <code>after_commit</code> callback, you
will receive a deprecation warning about this upcoming change. When
you are ready, you can opt into the new behavior and remove the
deprecation warning by adding following configuration to your
<code>config/application.rb</code>:</p><div class="code_container">
<pre class="brush: plain; gutter: false; toolbar: false">
config.active_record.raise_in_transactional_callbacks = true
</pre>
</div>
<p>See <a href="https://github.com/rails/rails/pull/14488">#14488</a> and
<a href="https://github.com/rails/rails/pull/16537">#16537</a> for more details.</p><h4 id="ordering-of-test-cases">2.4 Ordering of test cases</h4><p>In Rails 5.0, test cases will be executed in random order by default. In
anticipation of this change, Rails 4.2 introduced a new configuration option
<code>active_support.test_order</code> for explicitly specifying the test ordering. This
allows you to either lock down the current behavior by setting the option to
<code>:sorted</code>, or opt into the future behavior by setting the option to <code>:random</code>.</p><p>If you do not specify a value for this option, a deprecation warning will be
emitted. To avoid this, add the following line to your test environment:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
# config/environments/test.rb
Rails.application.configure do
config.active_support.test_order = :sorted # or `:random` if you prefer
end
</pre>
</div>
<h4 id="serialized-attributes">2.5 Serialized attributes</h4><p>When using a custom coder (e.g. <code>serialize :metadata, JSON</code>),
assigning <code>nil</code> to a serialized attribute will save it to the database
as <code>NULL</code> instead of passing the <code>nil</code> value through the coder (e.g. <code>"null"</code>
when using the <code>JSON</code> coder).</p><h4 id="after-bundle-in-rails-templates">2.6 <code>after_bundle</code> in Rails templates</h4><p>If you have a Rails template that adds all the files in version control, it
fails to add the generated binstubs because it gets executed before Bundler:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
# template.rb
generate(:scaffold, "person name:string")
route "root to: 'people#index'"
rake("db:migrate")
git :init
git add: "."
git commit: %Q{ -m 'Initial commit' }
</pre>
</div>
<p>You can now wrap the <code>git</code> calls in an <code>after_bundle</code> block. It will be run
after the binstubs have been generated.</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
# template.rb
generate(:scaffold, "person name:string")
route "root to: 'people#index'"
rake("db:migrate")
after_bundle do
git :init
git add: "."
git commit: %Q{ -m 'Initial commit' }
end
</pre>
</div>
<h4 id="rails-html-sanitizer">2.7 Rails Html Sanitizer</h4><p>There's a new choice for sanitizing HTML fragments in your applications. The
venerable html-scanner approach is now officially being deprecated in favor of
<a href="https://github.com/rails/rails-html-sanitizer"><code>Rails Html Sanitizer</code></a>.</p><p>This means the methods <code>sanitize</code>, <code>sanitize_css</code>, <code>strip_tags</code> and
<code>strip_links</code> are backed by a new implementation.</p><p>This new sanitizer uses <a href="https://github.com/flavorjones/loofah">Loofah</a> internally. Loofah in turn uses Nokogiri, which
wraps XML parsers written in both C and Java, so sanitization should be faster
no matter which Ruby version you run.</p><p>The new version updates <code>sanitize</code>, so it can take a <code>Loofah::Scrubber</code> for
powerful scrubbing.
<a href="https://github.com/flavorjones/loofah#loofahscrubber">See some examples of scrubbers here</a>.</p><p>Two new scrubbers have also been added: <code>PermitScrubber</code> and <code>TargetScrubber</code>.
Read the <a href="https://github.com/rails/rails-html-sanitizer">gem's readme</a> for more information.</p><p>The documentation for <code>PermitScrubber</code> and <code>TargetScrubber</code> explains how you
can gain complete control over when and how elements should be stripped.</p><p>If your application needs to use the old behaviour, include <code>rails-deprecated_sanitizer</code> in your Gemfile:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
gem 'rails-deprecated_sanitizer'
</pre>
</div>
<h4 id="rails-dom-testing">2.8 Rails DOM Testing</h4><div class="todo"><p>Mention <a href="https://github.com/rails/rails/commit/4e97d7585a2f4788b9eed98c6cdaf4bb6f2cf5ce">https://github.com/rails/rails/commit/4e97d7585a2f4788b9eed98c6cdaf4bb6f2cf5ce</a></p></div><h3 id="upgrading-from-rails-4-0-to-rails-4-1">3 Upgrading from Rails 4.0 to Rails 4.1</h3><h4 id="csrf-protection-from-remote-script-tags">3.1 CSRF protection from remote <code><script></code> tags</h4><p>Or, "whaaat my tests are failing!!!?"</p><p>Cross-site request forgery (CSRF) protection now covers GET requests with
JavaScript responses, too. This prevents a third-party site from referencing
your JavaScript URL and attempting to run it to extract sensitive data.</p><p>This means that your functional and integration tests that use</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
get :index, format: :js
</pre>
</div>
<p>will now trigger CSRF protection. Switch to</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
xhr :get, :index, format: :js
</pre>
</div>
<p>to explicitly test an XmlHttpRequest.</p><p>If you really mean to load JavaScript from remote <code><script></code> tags, skip CSRF
protection on that action.</p><h4 id="spring">3.2 Spring</h4><p>If you want to use Spring as your application preloader you need to:</p>
<ol>
<li>Add <code>gem 'spring', group: :development</code> to your <code>Gemfile</code>.</li>
<li>Install spring using <code>bundle install</code>.</li>
<li>Springify your binstubs with <code>bundle exec spring binstub --all</code>.</li>
</ol>
<div class="note"><p>User defined rake tasks will run in the <code>development</code> environment by
default. If you want them to run in other environments consult the
<a href="https://github.com/rails/spring#rake">Spring README</a>.</p></div><h4 id="config-secrets-yml">3.3 <code>config/secrets.yml</code>
</h4><p>If you want to use the new <code>secrets.yml</code> convention to store your application's
secrets, you need to:</p>
<ol>
<li>
<p>Create a <code>secrets.yml</code> file in your <code>config</code> folder with the following content:</p>
<div class="code_container">
<pre class="brush: plain; gutter: false; toolbar: false">
development:
secret_key_base:
test:
secret_key_base:
production:
secret_key_base: <%= ENV["SECRET_KEY_BASE"] %>
</pre>
</div>
</li>
<li><p>Use your existing <code>secret_key_base</code> from the <code>secret_token.rb</code> initializer to
set the SECRET_KEY_BASE environment variable for whichever users running the
Rails application in production mode. Alternatively, you can simply copy the existing
<code>secret_key_base</code> from the <code>secret_token.rb</code> initializer to <code>secrets.yml</code>
under the <code>production</code> section, replacing '<%= ENV["SECRET_KEY_BASE"] %>'.</p></li>
<li><p>Remove the <code>secret_token.rb</code> initializer.</p></li>
<li><p>Use <code>rake secret</code> to generate new keys for the <code>development</code> and <code>test</code> sections.</p></li>
<li><p>Restart your server.</p></li>
</ol>
<h4 id="changes-to-test-helper">3.4 Changes to test helper</h4><p>If your test helper contains a call to
<code>ActiveRecord::Migration.check_pending!</code> this can be removed. The check
is now done automatically when you <code>require 'rails/test_help'</code>, although
leaving this line in your helper is not harmful in any way.</p><h4 id="cookies-serializer">3.5 Cookies serializer</h4><p>Applications created before Rails 4.1 uses <code>Marshal</code> to serialize cookie values into
the signed and encrypted cookie jars. If you want to use the new <code>JSON</code>-based format
in your application, you can add an initializer file with the following content:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
Rails.application.config.action_dispatch.cookies_serializer = :hybrid
</pre>
</div>
<p>This would transparently migrate your existing <code>Marshal</code>-serialized cookies into the
new <code>JSON</code>-based format.</p><p>When using the <code>:json</code> or <code>:hybrid</code> serializer, you should beware that not all
Ruby objects can be serialized as JSON. For example, <code>Date</code> and <code>Time</code> objects
will be serialized as strings, and <code>Hash</code>es will have their keys stringified.</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
class CookiesController < ApplicationController
def set_cookie
cookies.encrypted[:expiration_date] = Date.tomorrow # => Thu, 20 Mar 2014
redirect_to action: 'read_cookie'
end
def read_cookie
cookies.encrypted[:expiration_date] # => "2014-03-20"
end
end
</pre>
</div>
<p>It's advisable that you only store simple data (strings and numbers) in cookies.
If you have to store complex objects, you would need to handle the conversion
manually when reading the values on subsequent requests.</p><p>If you use the cookie session store, this would apply to the <code>session</code> and
<code>flash</code> hash as well.</p><h4 id="flash-structure-changes">3.6 Flash structure changes</h4><p>Flash message keys are
<a href="https://github.com/rails/rails/commit/a668beffd64106a1e1fedb71cc25eaaa11baf0c1">normalized to strings</a>. They
can still be accessed using either symbols or strings. Looping through the flash
will always yield string keys:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
flash["string"] = "a string"
flash[:symbol] = "a symbol"
# Rails < 4.1
flash.keys # => ["string", :symbol]
# Rails >= 4.1
flash.keys # => ["string", "symbol"]
</pre>
</div>
<p>Make sure you are comparing Flash message keys against strings.</p><h4 id="changes-in-json-handling">3.7 Changes in JSON handling</h4><p>There are a few major changes related to JSON handling in Rails 4.1.</p><h5 id="multijson-removal">3.7.1 MultiJSON removal</h5><p>MultiJSON has reached its <a href="https://github.com/rails/rails/pull/10576">end-of-life</a>
and has been removed from Rails.</p><p>If your application currently depend on MultiJSON directly, you have a few options:</p>
<ol>
<li><p>Add 'multi_json' to your Gemfile. Note that this might cease to work in the future</p></li>
<li><p>Migrate away from MultiJSON by using <code>obj.to_json</code>, and <code>JSON.parse(str)</code> instead.</p></li>
</ol>
<div class="warning"><p>Do not simply replace <code>MultiJson.dump</code> and <code>MultiJson.load</code> with
<code>JSON.dump</code> and <code>JSON.load</code>. These JSON gem APIs are meant for serializing and
deserializing arbitrary Ruby objects and are generally <a href="http://www.ruby-doc.org/stdlib-2.0.0/libdoc/json/rdoc/JSON.html#method-i-load">unsafe</a>.</p></div><h5 id="json-gem-compatibility">3.7.2 JSON gem compatibility</h5><p>Historically, Rails had some compatibility issues with the JSON gem. Using
<code>JSON.generate</code> and <code>JSON.dump</code> inside a Rails application could produce
unexpected errors.</p><p>Rails 4.1 fixed these issues by isolating its own encoder from the JSON gem. The
JSON gem APIs will function as normal, but they will not have access to any
Rails-specific features. For example:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
class FooBar
def as_json(options = nil)
{ foo: 'bar' }
end
end
>> FooBar.new.to_json # => "{\"foo\":\"bar\"}"
>> JSON.generate(FooBar.new, quirks_mode: true) # => "\"#<FooBar:0x007fa80a481610>\""
</pre>
</div>
<h5 id="new-json-encoder">3.7.3 New JSON encoder</h5><p>The JSON encoder in Rails 4.1 has been rewritten to take advantage of the JSON
gem. For most applications, this should be a transparent change. However, as
part of the rewrite, the following features have been removed from the encoder:</p>
<ol>
<li>Circular data structure detection</li>
<li>Support for the <code>encode_json</code> hook</li>
<li>Option to encode <code>BigDecimal</code> objects as numbers instead of strings</li>
</ol>
<p>If your application depends on one of these features, you can get them back by
adding the <a href="https://github.com/rails/activesupport-json_encoder"><code>activesupport-json_encoder</code></a>
gem to your Gemfile.</p><h5 id="json-representation-of-time-objects">3.7.4 JSON representation of Time objects</h5><p><code>#as_json</code> for objects with time component (<code>Time</code>, <code>DateTime</code>, <code>ActiveSupport::TimeWithZone</code>)
now returns millisecond precision by default. If you need to keep old behavior with no millisecond
precision, set the following in an initializer:</p><div class="code_container">
<pre class="brush: plain; gutter: false; toolbar: false">
ActiveSupport::JSON::Encoding.time_precision = 0
</pre>
</div>
<h4 id="usage-of-return-within-inline-callback-blocks">3.8 Usage of <code>return</code> within inline callback blocks</h4><p>Previously, Rails allowed inline callback blocks to use <code>return</code> this way:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
class ReadOnlyModel < ActiveRecord::Base
before_save { return false } # BAD
end
</pre>
</div>
<p>This behaviour was never intentionally supported. Due to a change in the internals
of <code>ActiveSupport::Callbacks</code>, this is no longer allowed in Rails 4.1. Using a
<code>return</code> statement in an inline callback block causes a <code>LocalJumpError</code> to
be raised when the callback is executed.</p><p>Inline callback blocks using <code>return</code> can be refactored to evaluate to the
returned value:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
class ReadOnlyModel < ActiveRecord::Base
before_save { false } # GOOD
end
</pre>
</div>
<p>Alternatively, if <code>return</code> is preferred it is recommended to explicitly define
a method:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
class ReadOnlyModel < ActiveRecord::Base
before_save :before_save_callback # GOOD
private
def before_save_callback
return false
end
end
</pre>
</div>
<p>This change applies to most places in Rails where callbacks are used, including
Active Record and Active Model callbacks, as well as filters in Action
Controller (e.g. <code>before_action</code>).</p><p>See <a href="https://github.com/rails/rails/pull/13271">this pull request</a> for more
details.</p><h4 id="methods-defined-in-active-record-fixtures">3.9 Methods defined in Active Record fixtures</h4><p>Rails 4.1 evaluates each fixture's ERB in a separate context, so helper methods
defined in a fixture will not be available in other fixtures.</p><p>Helper methods that are used in multiple fixtures should be defined on modules
included in the newly introduced <code>ActiveRecord::FixtureSet.context_class</code>, in
<code>test_helper.rb</code>.</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
module FixtureFileHelpers
def file_sha(path)
Digest::SHA2.hexdigest(File.read(Rails.root.join('test/fixtures', path)))
end
end
ActiveRecord::FixtureSet.context_class.send :include, FixtureFileHelpers
</pre>
</div>
<h4 id="i18n-enforcing-available-locales">3.10 I18n enforcing available locales</h4><p>Rails 4.1 now defaults the I18n option <code>enforce_available_locales</code> to <code>true</code>. This
means that it will make sure that all locales passed to it must be declared in
the <code>available_locales</code> list.</p><p>To disable it (and allow I18n to accept <em>any</em> locale option) add the following
configuration to your application:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
config.i18n.enforce_available_locales = false
</pre>
</div>
<p>Note that this option was added as a security measure, to ensure user input
cannot be used as locale information unless it is previously known. Therefore,
it's recommended not to disable this option unless you have a strong reason for
doing so.</p><h4 id="mutator-methods-called-on-relation">3.11 Mutator methods called on Relation</h4><p><code>Relation</code> no longer has mutator methods like <code>#map!</code> and <code>#delete_if</code>. Convert
to an <code>Array</code> by calling <code>#to_a</code> before using these methods.</p><p>It intends to prevent odd bugs and confusion in code that call mutator
methods directly on the <code>Relation</code>.</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
# Instead of this
Author.where(name: 'Hank Moody').compact!
# Now you have to do this
authors = Author.where(name: 'Hank Moody').to_a
authors.compact!
</pre>
</div>
<h4 id="changes-on-default-scopes">3.12 Changes on Default Scopes</h4><p>Default scopes are no longer overridden by chained conditions.</p><p>In previous versions when you defined a <code>default_scope</code> in a model
it was overridden by chained conditions in the same field. Now it
is merged like any other scope.</p><p>Before:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
class User < ActiveRecord::Base
default_scope { where state: 'pending' }
scope :active, -> { where state: 'active' }
scope :inactive, -> { where state: 'inactive' }
end
User.all
# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending'
User.active
# SELECT "users".* FROM "users" WHERE "users"."state" = 'active'
User.where(state: 'inactive')
# SELECT "users".* FROM "users" WHERE "users"."state" = 'inactive'
</pre>
</div>
<p>After:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
class User < ActiveRecord::Base
default_scope { where state: 'pending' }
scope :active, -> { where state: 'active' }
scope :inactive, -> { where state: 'inactive' }
end
User.all
# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending'
User.active
# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending' AND "users"."state" = 'active'
User.where(state: 'inactive')
# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending' AND "users"."state" = 'inactive'
</pre>
</div>
<p>To get the previous behavior it is needed to explicitly remove the
<code>default_scope</code> condition using <code>unscoped</code>, <code>unscope</code>, <code>rewhere</code> or
<code>except</code>.</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
class User < ActiveRecord::Base
default_scope { where state: 'pending' }
scope :active, -> { unscope(where: :state).where(state: 'active') }
scope :inactive, -> { rewhere state: 'inactive' }
end
User.all
# SELECT "users".* FROM "users" WHERE "users"."state" = 'pending'
User.active
# SELECT "users".* FROM "users" WHERE "users"."state" = 'active'
User.inactive
# SELECT "users".* FROM "users" WHERE "users"."state" = 'inactive'
</pre>
</div>
<h4 id="rendering-content-from-string">3.13 Rendering content from string</h4><p>Rails 4.1 introduces <code>:plain</code>, <code>:html</code>, and <code>:body</code> options to <code>render</code>. Those
options are now the preferred way to render string-based content, as it allows
you to specify which content type you want the response sent as.</p>
<ul>
<li>
<code>render :plain</code> will set the content type to <code>text/plain</code>
</li>
<li>
<code>render :html</code> will set the content type to <code>text/html</code>
</li>
<li>
<code>render :body</code> will <em>not</em> set the content type header.</li>
</ul>
<p>From the security standpoint, if you don't expect to have any markup in your
response body, you should be using <code>render :plain</code> as most browsers will escape
unsafe content in the response for you.</p><p>We will be deprecating the use of <code>render :text</code> in a future version. So please
start using the more precise <code>:plain:</code>, <code>:html</code>, and <code>:body</code> options instead.
Using <code>render :text</code> may pose a security risk, as the content is sent as
<code>text/html</code>.</p><h4 id="postgresql-json-and-hstore-datatypes">3.14 PostgreSQL json and hstore datatypes</h4><p>Rails 4.1 will map <code>json</code> and <code>hstore</code> columns to a string-keyed Ruby <code>Hash</code>.
In earlier versions, a <code>HashWithIndifferentAccess</code> was used. This means that
symbol access is no longer supported. This is also the case for
<code>store_accessors</code> based on top of <code>json</code> or <code>hstore</code> columns. Make sure to use
string keys consistently.</p><h4 id="explicit-block-use-for-activesupport-callbacks">3.15 Explicit block use for <code>ActiveSupport::Callbacks</code>
</h4><p>Rails 4.1 now expects an explicit block to be passed when calling
<code>ActiveSupport::Callbacks.set_callback</code>. This change stems from
<code>ActiveSupport::Callbacks</code> being largely rewritten for the 4.1 release.</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
# Previously in Rails 4.0
set_callback :save, :around, ->(r, &block) { stuff; result = block.call; stuff }
# Now in Rails 4.1
set_callback :save, :around, ->(r, block) { stuff; result = block.call; stuff }
</pre>
</div>
<h3 id="upgrading-from-rails-3-2-to-rails-4-0">4 Upgrading from Rails 3.2 to Rails 4.0</h3><p>If your application is currently on any version of Rails older than 3.2.x, you should upgrade to Rails 3.2 before attempting one to Rails 4.0.</p><p>The following changes are meant for upgrading your application to Rails 4.0.</p><h4 id="http-patch">4.1 HTTP PATCH</h4><p>Rails 4 now uses <code>PATCH</code> as the primary HTTP verb for updates when a RESTful
resource is declared in <code>config/routes.rb</code>. The <code>update</code> action is still used,
and <code>PUT</code> requests will continue to be routed to the <code>update</code> action as well.
So, if you're using only the standard RESTful routes, no changes need to be made:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
resources :users
</pre>
</div>
<div class="code_container">
<pre class="brush: ruby; html-script: true; gutter: false; toolbar: false">
<%= form_for @user do |f| %>
</pre>
</div>
<div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
class UsersController < ApplicationController
def update
# No change needed; PATCH will be preferred, and PUT will still work.
end
end
</pre>
</div>
<p>However, you will need to make a change if you are using <code>form_for</code> to update
a resource in conjunction with a custom route using the <code>PUT</code> HTTP method:</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
resources :users, do
put :update_name, on: :member
end
</pre>
</div>
<div class="code_container">
<pre class="brush: ruby; html-script: true; gutter: false; toolbar: false">
<%= form_for [ :update_name, @user ] do |f| %>
</pre>
</div>
<div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
class UsersController < ApplicationController
def update_name
# Change needed; form_for will try to use a non-existent PATCH route.
end
end
</pre>
</div>
<p>If the action is not being used in a public API and you are free to change the
HTTP method, you can update your route to use <code>patch</code> instead of <code>put</code>:</p><p><code>PUT</code> requests to <code>/users/:id</code> in Rails 4 get routed to <code>update</code> as they are
today. So, if you have an API that gets real PUT requests it is going to work.
The router also routes <code>PATCH</code> requests to <code>/users/:id</code> to the <code>update</code> action.</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
resources :users do
patch :update_name, on: :member
end
</pre>
</div>
<p>If the action is being used in a public API and you can't change to HTTP method
being used, you can update your form to use the <code>PUT</code> method instead:</p><div class="code_container">
<pre class="brush: ruby; html-script: true; gutter: false; toolbar: false">
<%= form_for [ :update_name, @user ], method: :put do |f| %>
</pre>
</div>
<p>For more on PATCH and why this change was made, see <a href="http://weblog.rubyonrails.org/2012/2/26/edge-rails-patch-is-the-new-primary-http-method-for-updates/">this post</a>
on the Rails blog.</p><h5 id="a-note-about-media-types">4.1.1 A note about media types</h5><p>The errata for the <code>PATCH</code> verb <a href="http://www.rfc-editor.org/errata_search.php?rfc=5789">specifies that a 'diff' media type should be
used with <code>PATCH</code></a>. One
such format is <a href="http://tools.ietf.org/html/rfc6902">JSON Patch</a>. While Rails
does not support JSON Patch natively, it's easy enough to add support:</p><div class="code_container">
<pre class="brush: plain; gutter: false; toolbar: false">
# in your controller
def update
respond_to do |format|
format.json do
# perform a partial update
@article.update params[:article]
end
format.json_patch do
# perform sophisticated change
end
end
end
# In config/initializers/json_patch.rb:
Mime::Type.register 'application/json-patch+json', :json_patch
</pre>
</div>
<p>As JSON Patch was only recently made into an RFC, there aren't a lot of great
Ruby libraries yet. Aaron Patterson's
<a href="https://github.com/tenderlove/hana">hana</a> is one such gem, but doesn't have
full support for the last few changes in the specification.</p><h4 id="upgrading-from-rails-3-2-to-rails-4-0-gemfile">4.2 Gemfile</h4><p>Rails 4.0 removed the <code>assets</code> group from Gemfile. You'd need to remove that
line from your Gemfile when upgrading. You should also update your application
file (in <code>config/application.rb</code>):</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
# Require the gems listed in Gemfile, including any gems
# you've limited to :test, :development, or :production.
Bundler.require(:default, Rails.env)
</pre>
</div>
<h4 id="upgrading-from-rails-3-2-to-rails-4-0-vendor-plugins">4.3 vendor/plugins</h4><p>Rails 4.0 no longer supports loading plugins from <code>vendor/plugins</code>. You must replace any plugins by extracting them to gems and adding them to your Gemfile. If you choose not to make them gems, you can move them into, say, <code>lib/my_plugin/*</code> and add an appropriate initializer in <code>config/initializers/my_plugin.rb</code>.</p><h4 id="upgrading-from-rails-3-2-to-rails-4-0-active-record">4.4 Active Record</h4>
<ul>
<li><p>Rails 4.0 has removed the identity map from Active Record, due to <a href="https://github.com/rails/rails/commit/302c912bf6bcd0fa200d964ec2dc4a44abe328a6">some inconsistencies with associations</a>. If you have manually enabled it in your application, you will have to remove the following config that has no effect anymore: <code>config.active_record.identity_map</code>.</p></li>
<li><p>The <code>delete</code> method in collection associations can now receive <code>Fixnum</code> or <code>String</code> arguments as record ids, besides records, pretty much like the <code>destroy</code> method does. Previously it raised <code>ActiveRecord::AssociationTypeMismatch</code> for such arguments. From Rails 4.0 on <code>delete</code> automatically tries to find the records matching the given ids before deleting them.</p></li>
<li><p>In Rails 4.0 when a column or a table is renamed the related indexes are also renamed. If you have migrations which rename the indexes, they are no longer needed.</p></li>
<li><p>Rails 4.0 has changed <code>serialized_attributes</code> and <code>attr_readonly</code> to class methods only. You shouldn't use instance methods since it's now deprecated. You should change them to use class methods, e.g. <code>self.serialized_attributes</code> to <code>self.class.serialized_attributes</code>.</p></li>
<li><p>When using the default coder, assigning <code>nil</code> to a serialized attribute will save it
to the database as <code>NULL</code> instead of passing the <code>nil</code> value through YAML (<code>"--- \n...\n"</code>).</p></li>
<li><p>Rails 4.0 has removed <code>attr_accessible</code> and <code>attr_protected</code> feature in favor of Strong Parameters. You can use the <a href="https://github.com/rails/protected_attributes">Protected Attributes gem</a> for a smooth upgrade path.</p></li>
<li><p>If you are not using Protected Attributes, you can remove any options related to
this gem such as <code>whitelist_attributes</code> or <code>mass_assignment_sanitizer</code> options.</p></li>
<li><p>Rails 4.0 requires that scopes use a callable object such as a Proc or lambda:</p></li>
</ul>
<div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
scope :active, where(active: true)
# becomes
scope :active, -> { where active: true }
</pre>
</div>
<ul>
<li><p>Rails 4.0 has deprecated <code>ActiveRecord::Fixtures</code> in favor of <code>ActiveRecord::FixtureSet</code>.</p></li>
<li><p>Rails 4.0 has deprecated <code>ActiveRecord::TestCase</code> in favor of <code>ActiveSupport::TestCase</code>.</p></li>
<li><p>Rails 4.0 has deprecated the old-style hash based finder API. This means that
methods which previously accepted "finder options" no longer do.</p></li>
<li>
<p>All dynamic methods except for <code>find_by_...</code> and <code>find_by_...!</code> are deprecated.
Here's how you can handle the changes:</p>
<ul>
<li>
<code>find_all_by_...</code> becomes <code>where(...)</code>.</li>
<li>
<code>find_last_by_...</code> becomes <code>where(...).last</code>.</li>
<li>
<code>scoped_by_...</code> becomes <code>where(...)</code>.</li>
<li>
<code>find_or_initialize_by_...</code> becomes <code>find_or_initialize_by(...)</code>.</li>
<li>
<code>find_or_create_by_...</code> becomes <code>find_or_create_by(...)</code>.</li>
</ul>
</li>
<li><p>Note that <code>where(...)</code> returns a relation, not an array like the old finders. If you require an <code>Array</code>, use <code>where(...).to_a</code>.</p></li>
<li><p>These equivalent methods may not execute the same SQL as the previous implementation.</p></li>
<li><p>To re-enable the old finders, you can use the <a href="https://github.com/rails/activerecord-deprecated_finders">activerecord-deprecated_finders gem</a>.</p></li>
</ul>
<h4 id="active-resource">4.5 Active Resource</h4><p>Rails 4.0 extracted Active Resource to its own gem. If you still need the feature you can add the <a href="https://github.com/rails/activeresource">Active Resource gem</a> in your Gemfile.</p><h4 id="active-model">4.6 Active Model</h4>
<ul>
<li><p>Rails 4.0 has changed how errors attach with the <code>ActiveModel::Validations::ConfirmationValidator</code>. Now when confirmation validations fail, the error will be attached to <code>:#{attribute}_confirmation</code> instead of <code>attribute</code>.</p></li>
<li><p>Rails 4.0 has changed <code>ActiveModel::Serializers::JSON.include_root_in_json</code> default value to <code>false</code>. Now, Active Model Serializers and Active Record objects have the same default behaviour. This means that you can comment or remove the following option in the <code>config/initializers/wrap_parameters.rb</code> file:</p></li>
</ul>
<div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
# Disable root element in JSON by default.
# ActiveSupport.on_load(:active_record) do
# self.include_root_in_json = false
# end
</pre>
</div>
<h4 id="action-pack">4.7 Action Pack</h4>
<ul>
<li>Rails 4.0 introduces <code>ActiveSupport::KeyGenerator</code> and uses this as a base from which to generate and verify signed cookies (among other things). Existing signed cookies generated with Rails 3.x will be transparently upgraded if you leave your existing <code>secret_token</code> in place and add the new <code>secret_key_base</code>.</li>
</ul>
<div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
# config/initializers/secret_token.rb
Myapp::Application.config.secret_token = 'existing secret token'
Myapp::Application.config.secret_key_base = 'new secret key base'
</pre>
</div>
<p>Please note that you should wait to set <code>secret_key_base</code> until you have 100% of your userbase on Rails 4.x and are reasonably sure you will not need to rollback to Rails 3.x. This is because cookies signed based on the new <code>secret_key_base</code> in Rails 4.x are not backwards compatible with Rails 3.x. You are free to leave your existing <code>secret_token</code> in place, not set the new <code>secret_key_base</code>, and ignore the deprecation warnings until you are reasonably sure that your upgrade is otherwise complete.</p><p>If you are relying on the ability for external applications or Javascript to be able to read your Rails app's signed session cookies (or signed cookies in general) you should not set <code>secret_key_base</code> until you have decoupled these concerns.</p>
<ul>
<li>Rails 4.0 encrypts the contents of cookie-based sessions if <code>secret_key_base</code> has been set. Rails 3.x signed, but did not encrypt, the contents of cookie-based session. Signed cookies are "secure" in that they are verified to have been generated by your app and are tamper-proof. However, the contents can be viewed by end users, and encrypting the contents eliminates this caveat/concern without a significant performance penalty.</li>
</ul>
<p>Please read <a href="https://github.com/rails/rails/pull/9978">Pull Request #9978</a> for details on the move to encrypted session cookies.</p>
<ul>
<li><p>Rails 4.0 removed the <code>ActionController::Base.asset_path</code> option. Use the assets pipeline feature.</p></li>
<li><p>Rails 4.0 has deprecated <code>ActionController::Base.page_cache_extension</code> option. Use <code>ActionController::Base.default_static_extension</code> instead.</p></li>
<li><p>Rails 4.0 has removed Action and Page caching from Action Pack. You will need to add the <code>actionpack-action_caching</code> gem in order to use <code>caches_action</code> and the <code>actionpack-page_caching</code> to use <code>caches_pages</code> in your controllers.</p></li>
<li><p>Rails 4.0 has removed the XML parameters parser. You will need to add the <code>actionpack-xml_parser</code> gem if you require this feature.</p></li>
<li><p>Rails 4.0 changes the default memcached client from <code>memcache-client</code> to <code>dalli</code>. To upgrade, simply add <code>gem 'dalli'</code> to your <code>Gemfile</code>.</p></li>
<li><p>Rails 4.0 deprecates the <code>dom_id</code> and <code>dom_class</code> methods in controllers (they are fine in views). You will need to include the <code>ActionView::RecordIdentifier</code> module in controllers requiring this feature.</p></li>
<li><p>Rails 4.0 deprecates the <code>:confirm</code> option for the <code>link_to</code> helper. You should
instead rely on a data attribute (e.g. <code>data: { confirm: 'Are you sure?' }</code>).
This deprecation also concerns the helpers based on this one (such as <code>link_to_if</code>
or <code>link_to_unless</code>).</p></li>
<li><p>Rails 4.0 changed how <code>assert_generates</code>, <code>assert_recognizes</code>, and <code>assert_routing</code> work. Now all these assertions raise <code>Assertion</code> instead of <code>ActionController::RoutingError</code>.</p></li>
<li><p>Rails 4.0 raises an <code>ArgumentError</code> if clashing named routes are defined. This can be triggered by explicitly defined named routes or by the <code>resources</code> method. Here are two examples that clash with routes named <code>example_path</code>:</p></li>
</ul>
<div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
get 'one' => 'test#example', as: :example
get 'two' => 'test#example', as: :example
</pre>
</div>
<div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
resources :examples
get 'clashing/:id' => 'test#example', as: :example
</pre>
</div>
<p>In the first case, you can simply avoid using the same name for multiple
routes. In the second, you can use the <code>only</code> or <code>except</code> options provided by
the <code>resources</code> method to restrict the routes created as detailed in the
<a href="routing.html#restricting-the-routes-created">Routing Guide</a>.</p>
<ul>
<li>Rails 4.0 also changed the way unicode character routes are drawn. Now you can draw unicode character routes directly. If you already draw such routes, you must change them, for example:</li>
</ul>
<div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
get Rack::Utils.escape('こんにちは'), controller: 'welcome', action: 'index'
</pre>
</div>
<p>becomes</p><div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
get 'こんにちは', controller: 'welcome', action: 'index'
</pre>
</div>
<ul>
<li>Rails 4.0 requires that routes using <code>match</code> must specify the request method. For example:</li>
</ul>
<div class="code_container">
<pre class="brush: ruby; gutter: false; toolbar: false">
# Rails 3.x
match '/' => 'root#index'
# becomes
match '/' => 'root#index', via: :get