order on the old ones The previous behavior added a major backward incompatibility since it impossible to have a upgrade path without major changes on the application code. We are taking the most conservative path to be consistent with the idea of having a smoother upgrade on Rails 4. We are reverting the behavior for what was in Rails 3.x and, if needed, we will implement a new API to prepend the order clauses in Rails 4.1.
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A Guide for Upgrading Ruby on Rails
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.
General Advice
Before attempting to upgrade an existing application, you should be sure you have a good reason to upgrade. You need to balance out 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.
Test Coverage
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 before you start an upgrade.
Ruby Versions
Rails generally stays close to the latest released Ruby version when it's released:
- 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.
- Rails 3.2.x is the last branch to support Ruby 1.8.7.
- Rails 4 prefers Ruby 2.0 and requires 1.9.3 or newer.
TIP: 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.
HTTP PATCH
Rails 4 now uses PATCH
as the primary HTTP verb for updates when a RESTful
resource is declared in config/routes.rb
. The update
action is still used,
and PUT
requests will continue to be routed to the update
action as well.
So, if you're using only the standard RESTful routes, no changes need to be made:
resources :users
<%= form_for @user do |f| %>
class UsersController < ApplicationController
def update
# No change needed; PATCH will be preferred, and PUT will still work.
end
end
However, you will need to make a change if you are using form_for
to update
a resource in conjunction with a custom route using the PUT
HTTP method:
resources :users, do
put :update_name, on: :member
end
<%= form_for [ :update_name, @user ] do |f| %>
class UsersController < ApplicationController
def update_name
# Change needed; form_for will try to use a non-existent PATCH route.
end
end
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 patch
instead of put
:
PUT
requests to /users/:id
in Rails 4 get routed to update
as they are
today. So, if you have an API that gets real PUT requests it is going to work.
The router also routes PATCH
requests to /users/:id
to the update
action.
resources :users do
patch :update_name, on: :member
end
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 PUT
method instead:
<%= form_for [ :update_name, @user ], method: :put do |f| %>
For more on PATCH and why this change was made, see this post on the Rails blog.
A note about media types
The errata for the PATCH
verb specifies that a 'diff' media type should be
used with PATCH
. One
such format is JSON Patch. While Rails
does not support JSON Patch natively, it's easy enough to add support:
# in your controller
def update
respond_to do |format|
format.json do
# perform a partial update
@post.update params[:post]
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
As JSON Patch was only recently made into an RFC, there aren't a lot of great Ruby libraries yet. Aaron Patterson's hana is one such gem, but doesn't have full support for the last few changes in the specification.
Upgrading from Rails 3.2 to Rails 4.0
NOTE: This section is a work in progress.
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.
The following changes are meant for upgrading your application to Rails 4.0.
Gemfile
Rails 4.0 removed the assets
group from Gemfile. You'd need to remove that
line from your Gemfile when upgrading. You should also update your application
file (in config/application.rb
):
# Require the gems listed in Gemfile, including any gems
# you've limited to :test, :development, or :production.
Bundler.require(:default, Rails.env)
vendor/plugins
Rails 4.0 no longer supports loading plugins from vendor/plugins
. 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, lib/my_plugin/*
and add an appropriate initializer in config/initializers/my_plugin.rb
.
Active Record
-
Rails 4.0 has removed the identity map from Active Record, due to some inconsistencies with associations. If you have manually enabled it in your application, you will have to remove the following config that has no effect anymore:
config.active_record.identity_map
. -
The
delete
method in collection associations can now receiveFixnum
orString
arguments as record ids, besides records, pretty much like thedestroy
method does. Previously it raisedActiveRecord::AssociationTypeMismatch
for such arguments. From Rails 4.0 ondelete
automatically tries to find the records matching the given ids before deleting them. -
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.
-
Rails 4.0 has changed
serialized_attributes
andattr_readonly
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.self.serialized_attributes
toself.class.serialized_attributes
. -
Rails 4.0 has removed
attr_accessible
andattr_protected
feature in favor of Strong Parameters. You can use the Protected Attributes gem for a smooth upgrade path. -
If you are not using Protected Attributes, you can remove any options related to this gem such as
whitelist_attributes
ormass_assignment_sanitizer
options. -
Rails 4.0 requires that scopes use a callable object such as a Proc or lambda:
scope :active, where(active: true)
# becomes
scope :active, -> { where active: true }
- Rails 4.0 has deprecated
ActiveRecord::Fixtures
in favor ofActiveRecord::FixtureSet
. - Rails 4.0 has deprecated
ActiveRecord::TestCase
in favor ofActiveSupport::TestCase
.
Active Resource
Rails 4.0 extracted Active Resource to its own gem. If you still need the feature you can add the Active Resource gem in your Gemfile.
Active Model
-
Rails 4.0 has changed how errors attach with the
ActiveModel::Validations::ConfirmationValidator
. Now when confirmation validations fail, the error will be attached to:#{attribute}_confirmation
instead ofattribute
. -
Rails 4.0 has changed
ActiveModel::Serializers::JSON.include_root_in_json
default value tofalse
. 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 theconfig/initializers/wrap_parameters.rb
file:
# Disable root element in JSON by default.
# ActiveSupport.on_load(:active_record) do
# self.include_root_in_json = false
# end
Action Pack
- Rails 4.0 introduces
ActiveSupport::KeyGenerator
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 existingsecret_token
in place and add the newsecret_key_base
.
# config/initializers/secret_token.rb
Myapp::Application.config.secret_token = 'existing secret token'
Myapp::Application.config.secret_key_base = 'new secret key base'
Please note that you should wait to set secret_key_base
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 secret_key_base
in Rails 4.x are not backwards compatible with Rails 3.x. You are free to leave your existing secret_token
in place, not set the new secret_key_base
, and ignore the deprecation warnings until you are reasonably sure that your upgrade is otherwise complete.
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 secret_key_base
until you have decoupled these concerns.
- Rails 4.0 encrypts the contents of cookie-based sessions if
secret_key_base
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.
Please read Pull Request #9978 for details on the move to encrypted session cookies.
-
Rails 4.0 removed the
ActionController::Base.asset_path
option. Use the assets pipeline feature. -
Rails 4.0 has deprecated
ActionController::Base.page_cache_extension
option. UseActionController::Base.default_static_extension
instead. -
Rails 4.0 has removed Action and Page caching from Action Pack. You will need to add the
actionpack-action_caching
gem in order to usecaches_action
and theactionpack-page_caching
to usecaches_pages
in your controllers. -
Rails 4.0 has removed the XML parameters parser. You will need to add the
actionpack-xml_parser
gem if you require this feature. -
Rails 4.0 changes the default memcached client from
memcache-client
todalli
. To upgrade, simply addgem 'dalli'
to yourGemfile
. -
Rails 4.0 deprecates the
dom_id
anddom_class
methods in controllers (they are fine in views). You will need to include theActionView::RecordIdentifier
module in controllers requiring this feature. -
Rails 4.0 deprecates the
:confirm
option for thelink_to
helper. You should instead rely on a data attribute (e.g.data: { confirm: 'Are you sure?' }
). This deprecation also concerns the helpers based on this one (such aslink_to_if
orlink_to_unless
). -
Rails 4.0 changed how
assert_generates
,assert_recognizes
, andassert_routing
work. Now all these assertions raiseAssertion
instead ofActionController::RoutingError
. -
Rails 4.0 raises an
ArgumentError
if clashing named routes are defined. This can be triggered by explicitly defined named routes or by theresources
method. Here are two examples that clash with routes namedexample_path
:
get 'one' => 'test#example', as: :example
get 'two' => 'test#example', as: :example
resources :examples
get 'clashing/:id' => 'test#example', as: :example
In the first case, you can simply avoid using the same name for multiple
routes. In the second, you can use the only
or except
options provided by
the resources
method to restrict the routes created as detailed in the
Routing Guide.
- 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:
get Rack::Utils.escape('こんにちは'), controller: 'welcome', action: 'index'
becomes
get 'こんにちは', controller: 'welcome', action: 'index'
- Rails 4.0 requires that routes using
match
must specify the request method. For example:
# Rails 3.x
match "/" => "root#index"
# becomes
match "/" => "root#index", via: :get
# or
get "/" => "root#index"
- Rails 4.0 has removed
ActionDispatch::BestStandardsSupport
middleware,<!DOCTYPE html>
already triggers standards mode per http://msdn.microsoft.com/en-us/library/jj676915(v=vs.85).aspx and ChromeFrame header has been moved toconfig.action_dispatch.default_headers
.
Remember you must also remove any references to the middleware from your application code, for example:
# Raise exception
config.middleware.insert_before(Rack::Lock, ActionDispatch::BestStandardsSupport)
Also check your environment settings for config.action_dispatch.best_standards_support
and remove it if present.
-
In Rails 4.0, precompiling assets no longer automatically copies non-JS/CSS assets from
vendor/assets
andlib/assets
. Rails application and engine developers should put these assets inapp/assets
or configureconfig.assets.precompile
. -
In Rails 4.0,
ActionController::UnknownFormat
is raised when the action doesn't handle the request format. By default, the exception is handled by responding with 406 Not Acceptable, but you can override that now. In Rails 3, 406 Not Acceptable was always returned. No overrides. -
In Rails 4.0, a generic
ActionDispatch::ParamsParser::ParseError
exception is raised whenParamsParser
fails to parse request params. You will want to rescue this exception instead of the low-levelMultiJson::DecodeError
, for example. -
In Rails 4.0,
SCRIPT_NAME
is properly nested when engines are mounted on an app that's served from a URL prefix. You no longer have to setdefault_url_options[:script_name]
to work around overwritten URL prefixes. -
Rails 4.0 deprecated
ActionController::Integration
in favor ofActionDispatch::Integration
. -
Rails 4.0 deprecated
ActionController::IntegrationTest
in favor ofActionDispatch::IntegrationTest
. -
Rails 4.0 deprecated
ActionController::PerformanceTest
in favor ofActionDispatch::PerformanceTest
. -
Rails 4.0 deprecated
ActionController::AbstractRequest
in favor ofActionDispatch::Request
. -
Rails 4.0 deprecated
ActionController::Request
in favor ofActionDispatch::Request
. -
Rails 4.0 deprecated
ActionController::AbstractResponse
in favor ofActionDispatch::Response
. -
Rails 4.0 deprecated
ActionController::Response
in favor ofActionDispatch::Response
. -
Rails 4.0 deprecated
ActionController::Routing
in favor ofActionDispatch::Routing
.
Active Support
Rails 4.0 removes the j
alias for ERB::Util#json_escape
since j
is already used for ActionView::Helpers::JavaScriptHelper#escape_javascript
.
Helpers Loading Order
The order in which helpers from more than one directory are loaded has changed in Rails 4.0. Previously, they were gathered and then sorted alphabetically. After upgrading to Rails 4.0, helpers will preserve the order of loaded directories and will be sorted alphabetically only within each directory. Unless you explicitly use the helpers_path
parameter, this change will only impact the way of loading helpers from engines. If you rely on the ordering, you should check if correct methods are available after upgrade. If you would like to change the order in which engines are loaded, you can use config.railties_order=
method.
Active Record Observer and Action Controller Sweeper
Active Record Observer and Action Controller Sweeper have been extracted to the rails-observers
gem. You will need to add the rails-observers
gem if you require these features.
sprockets-rails
assets:precompile:primary
has been removed. Useassets:precompile
instead.- The
config.assets.compress
option should be changed toconfig.assets.js_compressor
like so for instance:
config.assets.js_compressor = :uglifier
sass-rails
asset-url
with two arguments is deprecated. For example:asset-url("rails.png", image)
becomesasset-url("rails.png")
Upgrading from Rails 3.1 to Rails 3.2
If your application is currently on any version of Rails older than 3.1.x, you should upgrade to Rails 3.1 before attempting an update to Rails 3.2.
The following changes are meant for upgrading your application to Rails 3.2.12, the latest 3.2.x version of Rails.
Gemfile
Make the following changes to your Gemfile
.
gem 'rails', '= 3.2.12'
group :assets do
gem 'sass-rails', '~> 3.2.3'
gem 'coffee-rails', '~> 3.2.1'
gem 'uglifier', '>= 1.0.3'
end
config/environments/development.rb
There are a couple of new configuration settings that you should add to your development environment:
# Raise exception on mass assignment protection for Active Record models
config.active_record.mass_assignment_sanitizer = :strict
# Log the query plan for queries taking more than this (works
# with SQLite, MySQL, and PostgreSQL)
config.active_record.auto_explain_threshold_in_seconds = 0.5
config/environments/test.rb
The mass_assignment_sanitizer
configuration setting should also be be added to config/environments/test.rb
:
# Raise exception on mass assignment protection for Active Record models
config.active_record.mass_assignment_sanitizer = :strict
vendor/plugins
Rails 3.2 deprecates vendor/plugins
and Rails 4.0 will remove them completely. While it's not strictly necessary as part of a Rails 3.2 upgrade, you can start replacing 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, lib/my_plugin/*
and add an appropriate initializer in config/initializers/my_plugin.rb
.
Upgrading from Rails 3.0 to Rails 3.1
If your application is currently on any version of Rails older than 3.0.x, you should upgrade to Rails 3.0 before attempting an update to Rails 3.1.
The following changes are meant for upgrading your application to Rails 3.1.11, the latest 3.1.x version of Rails.
Gemfile
Make the following changes to your Gemfile
.
gem 'rails', '= 3.1.11'
gem 'mysql2'
# Needed for the new asset pipeline
group :assets do
gem 'sass-rails', "~> 3.1.5"
gem 'coffee-rails', "~> 3.1.1"
gem 'uglifier', ">= 1.0.3"
end
# jQuery is the default JavaScript library in Rails 3.1
gem 'jquery-rails'
config/application.rb
The asset pipeline requires the following additions:
config.assets.enabled = true
config.assets.version = '1.0'
If your application is using an "/assets" route for a resource you may want change the prefix used for assets to avoid conflicts:
# Defaults to '/assets'
config.assets.prefix = '/asset-files'
config/environments/development.rb
Remove the RJS setting config.action_view.debug_rjs = true
.
Add these settings if you enable the asset pipeline:
# Do not compress assets
config.assets.compress = false
# Expands the lines which load the assets
config.assets.debug = true
config/environments/production.rb
Again, most of the changes below are for the asset pipeline. You can read more about these in the Asset Pipeline guide.
# Compress JavaScripts and CSS
config.assets.compress = true
# Don't fallback to assets pipeline if a precompiled asset is missed
config.assets.compile = false
# Generate digests for assets URLs
config.assets.digest = true
# Defaults to Rails.root.join("public/assets")
# config.assets.manifest = YOUR_PATH
# Precompile additional assets (application.js, application.css, and all non-JS/CSS are already added)
# config.assets.precompile += %w( search.js )
# Force all access to the app over SSL, use Strict-Transport-Security, and use secure cookies.
# config.force_ssl = true
config/environments/test.rb
You can help test performance with these additions to your test environment:
# Configure static asset server for tests with Cache-Control for performance
config.serve_static_assets = true
config.static_cache_control = "public, max-age=3600"
config/initializers/wrap_parameters.rb
Add this file with the following contents, if you wish to wrap parameters into a nested hash. This is on by default in new applications.
# Be sure to restart your server when you modify this file.
# This file contains settings for ActionController::ParamsWrapper which
# is enabled by default.
# Enable parameter wrapping for JSON. You can disable this by setting :format to an empty array.
ActiveSupport.on_load(:action_controller) do
wrap_parameters format: [:json]
end
# Disable root element in JSON by default.
ActiveSupport.on_load(:active_record) do
self.include_root_in_json = false
end
config/initializers/session_store.rb
You need to change your session key to something new, or remove all sessions:
# in config/initializers/session_store.rb
AppName::Application.config.session_store :cookie_store, key: 'SOMETHINGNEW'
or
$ rake db:sessions:clear
Remove :cache and :concat options in asset helpers references in views
- With the Asset Pipeline the :cache and :concat options aren't used anymore, delete these options from your views.