# 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.
### Chapters
1. [General Advice](#general-advice)
* [Test Coverage](#test-coverage)
* [Ruby Versions](#ruby-versions)
* [The Rake Task](#the-rake-task)
2. [Upgrading from Rails 4.1 to Rails 4.2](#upgrading-from-rails-4.1-to-rails-4.2)
3. [Upgrading from Rails 4.0 to Rails 4.1](#upgrading-from-rails-4.0-to-rails-4.1)
* [CSRF protection from remote `<script>` tags](#csrf-protection-from-remote-%3Cscript%3E-tags)
* [Spring](#spring)
* [`config/secrets.yml`](#config/secrets.yml)
* [Changes to test helper](#changes-to-test-helper)
* [Cookies serializer](#cookies-serializer)
* [Flash structure changes](#flash-structure-changes)
* [Changes in JSON handling](#changes-in-json-handling)
* [Usage of `return` within inline callback blocks](#usage-of-return-within-inline-callback-blocks)
* [Methods defined in Active Record fixtures](#methods-defined-in-active-record-fixtures)
* [I18n enforcing available locales](#i18n-enforcing-available-locales)
* [Mutator methods called on Relation](#mutator-methods-called-on-relation)
* [Changes on Default Scopes](#changes-on-default-scopes)
* [Rendering content from string](#rendering-content-from-string)
* [PostgreSQL json and hstore datatypes](#postgresql-json-and-hstore-datatypes)
* [Explicit block use for `ActiveSupport::Callbacks`](#explicit-block-use-for-activesupport::callbacks)
4. [Upgrading from Rails 3.2 to Rails 4.0](#upgrading-from-rails-3.2-to-rails-4.0)
* [HTTP PATCH](#http-patch)
* [Gemfile](#upgrading-from-rails-3.2-to-rails-4.0-gemfile)
* [vendor/plugins](#upgrading-from-rails-3.2-to-rails-4.0-vendor/plugins)
* [Active Record](#upgrading-from-rails-3.2-to-rails-4.0-active-record)
* [Active Resource](#active-resource)
* [Active Model](#active-model)
* [Action Pack](#action-pack)
* [Active Support](#active-support)
* [Helpers Loading Order](#helpers-loading-order)
* [Active Record Observer and Action Controller Sweeper](#active-record-observer-and-action-controller-sweeper)
* [sprockets-rails](#sprockets-rails)
* [sass-rails](#sass-rails)
5. [Upgrading from Rails 3.1 to Rails 3.2](#upgrading-from-rails-3.1-to-rails-3.2)
* [Gemfile](#upgrading-from-rails-3.1-to-rails-3.2-gemfile)
* [config/environments/development.rb](#upgrading-from-rails-3.1-to-rails-3.2-config/environments/development.rb)
* [config/environments/test.rb](#upgrading-from-rails-3.1-to-rails-3.2-config/environments/test.rb)
* [vendor/plugins](#upgrading-from-rails-3.1-to-rails-3.2-vendor/plugins)
* [Active Record](#upgrading-from-rails-3.1-to-rails-3.2-active-record)
6. [Upgrading from Rails 3.0 to Rails 3.1](#upgrading-from-rails-3.0-to-rails-3.1)
* [Gemfile](#gemfile)
* [config/application.rb](#config/application.rb)
* [config/environments/development.rb](#upgrading-from-rails-3.0-to-rails-3.1-config/environments/development.rb)
* [config/environments/production.rb](#config/environments/production.rb)
* [config/environments/test.rb](#upgrading-from-rails-3.0-to-rails-3.1-config/environments/test.rb)
* [config/initializers/wrap_parameters.rb](#config/initializers/wrap_parameters.rb)
* [config/initializers/session_store.rb](#config/initializers/session_store.rb)
* [Remove :cache and :concat options in asset helpers references in views](#remove-:cache-and-:concat-options-in-asset-helpers-references-in-views)
### 1 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.
#### 1.1 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.
#### 1.2 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.
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.
#### 1.3 The Rake Task
Rails provides the `rails:update` 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 a interactive session.
```
$ 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
...
```
Don't forget to review the difference, to see if there were any unexpected changes.
### 2 Upgrading from Rails 4.1 to Rails 4.2
This section is a work in progress.
### 3 Upgrading from Rails 4.0 to Rails 4.1
#### 3.1 CSRF protection from remote `<script>` tags
Or, "whaaat my tests are failing!!!?"
Cross-site request forgery (CSRF) protection now covers GET requests with JavaScript responses, too. That prevents a third-party site from referencing your JavaScript URL and attempting to run it to extract sensitive data.
This means that your functional and integration tests that use
```
get :index, format: :js
```
will now trigger CSRF protection. Switch to
```
xhr :get, :index, format: :js
```
to explicitly test an XmlHttpRequest.
If you really mean to load JavaScript from remote `<script>` tags, skip CSRF protection on that action.
#### 3.2 Spring
If you want to use Spring as your application preloader you need to:
1. Add `gem 'spring', group: :development` to your `Gemfile`.
2. Install spring using `bundle install`.
3. Springify your binstubs with `bundle exec spring binstub --all`.
User defined rake tasks will run in the `development` environment by default. If you want them to run in other environments consult the [Spring README](https://github.com/rails/spring#rake).
#### 3.3 `config/secrets.yml`
If you want to use the new `secrets.yml` convention to store your application's secrets, you need to:
1. Create a `secrets.yml` file in your `config` folder with the following content:
```
development:
secret_key_base:
test:
secret_key_base:
production:
secret_key_base: <%= ENV["SECRET_KEY_BASE"] %>
```
2. Use your existing `secret_key_base` from the `secret_token.rb` initializer to set the SECRET_KEY_BASE environment variable for whichever users run the Rails app in production mode. Alternately, you can simply copy the existing `secret_key_base` from the `secret_token.rb` initializer to `secrets.yml` under the `production` section, replacing '<%= ENV["SECRET_KEY_BASE"] %>'.
3. Remove the `secret_token.rb` initializer.
4. Use `rake secret` to generate new keys for the `development` and `test` sections.
5. Restart your server.
#### 3.4 Changes to test helper
If your test helper contains a call to `ActiveRecord::Migration.check_pending!` this can be removed. The check is now done automatically when you `require 'test_help'`, although leaving this line in your helper is not harmful in any way.
#### 3.5 Cookies serializer
Applications created before Rails 4.1 uses `Marshal` to serialize cookie values into the signed and encrypted cookie jars. If you want to use the new `JSON`-based format in your application, you can add an initializer file with the following content:
```
Rails.application.config.action_dispatch.cookies_serializer = :hybrid
```
This would transparently migrate your existing `Marshal`-serialized cookies into the new `JSON`-based format.
When using the `:json` or `:hybrid` serializer, you should beware that not all Ruby objects can be serialized as JSON. For example, `Date` and `Time` objects will be serialized as strings, and `Hash`es will have their keys stringified.
```
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
```
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.
If you use the cookie session store, this would apply to the `session` and `flash` hash as well.
#### 3.6 Flash structure changes
Flash message keys are [normalized to strings](https://github.com/rails/rails/commit/a668beffd64106a1e1fedb71cc25eaaa11baf0c1). They can still be accessed using either symbols or strings. Looping through the flash will always yield string keys:
```
flash["string"] = "a string"
flash[:symbol] = "a symbol"
# Rails < 4.1
flash.keys # => ["string", :symbol]
# Rails >= 4.1
flash.keys # => ["string", "symbol"]
```
Make sure you are comparing Flash message keys against strings.
#### 3.7 Changes in JSON handling
There are a few major changes related to JSON handling in Rails 4.1.
##### 3.7.1 MultiJSON removal
MultiJSON has reached its [end-of-life](https://github.com/rails/rails/pull/10576) and has been removed from Rails.
If your application currently depend on MultiJSON directly, you have a few options:
1. Add 'multi_json' to your Gemfile. Note that this might cease to work in the future
2. Migrate away from MultiJSON by using `obj.to_json`, and `JSON.parse(str)` instead.
Do not simply replace `MultiJson.dump` and `MultiJson.load` with `JSON.dump` and `JSON.load`. These JSON gem APIs are meant for serializing and deserializing arbitrary Ruby objects and are generally [unsafe](http://www.ruby-doc.org/stdlib-2.0.0/libdoc/json/rdoc/JSON.html#method-i-load).
##### 3.7.2 JSON gem compatibility
Historically, Rails had some compatibility issues with the JSON gem. Using `JSON.generate` and `JSON.dump` inside a Rails application could produce unexpected errors.
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:
```
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>\""
```
##### 3.7.3 New JSON encoder
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:
1. Circular data structure detection
2. Support for the `encode_json` hook
3. Option to encode `BigDecimal` objects as numbers instead of strings
If your application depends on one of these features, you can get them back by adding the [`activesupport-json_encoder`](https://github.com/rails/activesupport-json_encoder) gem to your Gemfile.
#### 3.8 Usage of `return` within inline callback blocks
Previously, Rails allowed inline callback blocks to use `return` this way:
```
class ReadOnlyModel < ActiveRecord::Base
before_save { return false } # BAD
end
```
This behaviour was never intentionally supported. Due to a change in the internals of `ActiveSupport::Callbacks`, this is no longer allowed in Rails 4.1\. Using a `return` statement in an inline callback block causes a `LocalJumpError` to be raised when the callback is executed.
Inline callback blocks using `return` can be refactored to evaluate to the returned value:
```
class ReadOnlyModel < ActiveRecord::Base
before_save { false } # GOOD
end
```
Alternatively, if `return` is preferred it is recommended to explicitly define a method:
```
class ReadOnlyModel < ActiveRecord::Base
before_save :before_save_callback # GOOD
private
def before_save_callback
return false
end
end
```
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. `before_action`).
See [this pull request](https://github.com/rails/rails/pull/13271) for more details.
#### 3.9 Methods defined in Active Record fixtures
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.
Helper methods that are used in multiple fixtures should be defined on modules included in the newly introduced `ActiveRecord::FixtureSet.context_class`, in `test_helper.rb`.
```
class 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
```
#### 3.10 I18n enforcing available locales
Rails 4.1 now defaults the I18n option `enforce_available_locales` to `true`, meaning that it will make sure that all locales passed to it must be declared in the `available_locales` list.
To disable it (and allow I18n to accept _any_ locale option) add the following configuration to your application:
```
config.i18n.enforce_available_locales = false
```
Note that this option was added as a security measure, to ensure user input could not be used as locale information unless previously known, so it's recommended not to disable this option unless you have a strong reason for doing so.
#### 3.11 Mutator methods called on Relation
`Relation` no longer has mutator methods like `#map!` and `#delete_if`. Convert to an `Array` by calling `#to_a` before using these methods.
It intends to prevent odd bugs and confusion in code that call mutator methods directly on the `Relation`.
```
# 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!
```
#### 3.12 Changes on Default Scopes
Default scopes are no longer overridden by chained conditions.
In previous versions when you defined a `default_scope` in a model it was overridden by chained conditions in the same field. Now it is merged like any other scope.
Before:
```
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'
```
After:
```
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'
```
To get the previous behavior it is needed to explicitly remove the `default_scope` condition using `unscoped`, `unscope`, `rewhere` or `except`.
```
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'
```
#### 3.13 Rendering content from string
Rails 4.1 introduces `:plain`, `:html`, and `:body` options to `render`. 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.
* `render :plain` will set the content type to `text/plain`
* `render :html` will set the content type to `text/html`
* `render :body` will _not_ set the content type header.
From the security standpoint, if you don't expect to have any markup in your response body, you should be using `render :plain` as most browsers will escape unsafe content in the response for you.
We will be deprecating the use of `render :text` in a future version. So please start using the more precise `:plain:`, `:html`, and `:body` options instead. Using `render :text` may pose a security risk, as the content is sent as `text/html`.
#### 3.14 PostgreSQL json and hstore datatypes
Rails 4.1 will map `json` and `hstore` columns to a string-keyed Ruby `Hash`. In earlier versions a `HashWithIndifferentAccess` was used. This means that symbol access is no longer supported. This is also the case for `store_accessors` based on top of `json` or `hstore` columns. Make sure to use string keys consistently.
#### 3.15 Explicit block use for `ActiveSupport::Callbacks`
Rails 4.1 now expects an explicit block to be passed when calling `ActiveSupport::Callbacks.set_callback`. This change stems from `ActiveSupport::Callbacks` being largely rewritten for the 4.1 release.
```
# 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 }
```
### 4 Upgrading from Rails 3.2 to Rails 4.0
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.
#### 4.1 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](http://weblog.rubyonrails.org/2012/2/25/edge-rails-patch-is-the-new-primary-http-method-for-updates/) on the Rails blog.
##### 4.1.1 A note about media types
The errata for the `PATCH` verb [specifies that a 'diff' media type should be used with `PATCH`](http://www.rfc-editor.org/errata_search.php?rfc=5789). One such format is [JSON Patch](http://tools.ietf.org/html/rfc6902). 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
@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
```
As JSON Patch was only recently made into an RFC, there aren't a lot of great Ruby libraries yet. Aaron Patterson's [hana](https://github.com/tenderlove/hana) is one such gem, but doesn't have full support for the last few changes in the specification.
#### 4.2 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)
```
#### 4.3 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`.
#### 4.4 Active Record
* Rails 4.0 has removed the identity map from Active Record, due to [some inconsistencies with associations](https://github.com/rails/rails/commit/302c912bf6bcd0fa200d964ec2dc4a44abe328a6). 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 receive `Fixnum` or `String` arguments as record ids, besides records, pretty much like the `destroy` method does. Previously it raised `ActiveRecord::AssociationTypeMismatch` for such arguments. From Rails 4.0 on `delete` 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` and `attr_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` to `self.class.serialized_attributes`.
* Rails 4.0 has removed `attr_accessible` and `attr_protected` feature in favor of Strong Parameters. You can use the [Protected Attributes gem](https://github.com/rails/protected_attributes) 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` or `mass_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 of `ActiveRecord::FixtureSet`.
* Rails 4.0 has deprecated `ActiveRecord::TestCase` in favor of `ActiveSupport::TestCase`.
* Rails 4.0 has 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_...` and `find_by_...!` are deprecated. Here's how you can handle the changes:
* `find_all_by_...` becomes `where(...)`.
* `find_last_by_...` becomes `where(...).last`.
* `scoped_by_...` becomes `where(...)`.
* `find_or_initialize_by_...` becomes `find_or_initialize_by(...)`.
* `find_or_create_by_...` becomes `find_or_create_by(...)`.
* Note that `where(...)` returns a relation, not an array like the old finders. If you require an `Array`, use `where(...).to_a`.
* These equivalent methods may not execute the same SQL as the previous implementation.
* To re-enable the old finders, you can use the [activerecord-deprecated_finders gem](https://github.com/rails/activerecord-deprecated_finders).
#### 4.5 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](https://github.com/rails/activeresource) in your Gemfile.
#### 4.6 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 of `attribute`.
* Rails 4.0 has changed `ActiveModel::Serializers::JSON.include_root_in_json` default value to `false`. 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 `config/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
```
#### 4.7 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 existing `secret_token` in place and add the new `secret_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](https://github.com/rails/rails/pull/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. Use `ActionController::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 use `caches_action` and the `actionpack-page_caching` to use `caches_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` to `dalli`. To upgrade, simply add `gem 'dalli'` to your `Gemfile`.
* Rails 4.0 deprecates the `dom_id` and `dom_class` methods in controllers (they are fine in views). You will need to include the `ActionView::RecordIdentifier` module in controllers requiring this feature.
* Rails 4.0 deprecates the `:confirm` option for the `link_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 as `link_to_if` or `link_to_unless`).
* Rails 4.0 changed how `assert_generates`, `assert_recognizes`, and `assert_routing` work. Now all these assertions raise `Assertion` instead of `ActionController::RoutingError`.
* Rails 4.0 raises an `ArgumentError` if clashing named routes are defined. This can be triggered by explicitly defined named routes or by the `resources` method. Here are two examples that clash with routes named `example_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](routing.html#restricting-the-routes-created).
* 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](http://msdn.microsoft.com/en-us/library/jj676915(v=vs.85).aspx) and ChromeFrame header has been moved to `config.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` and `lib/assets`. Rails application and engine developers should put these assets in `app/assets` or configure `config.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 when `ParamsParser` fails to parse request params. You will want to rescue this exception instead of the low-level `MultiJson::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 set `default_url_options[:script_name]` to work around overwritten URL prefixes.
* Rails 4.0 deprecated `ActionController::Integration` in favor of `ActionDispatch::Integration`.
* Rails 4.0 deprecated `ActionController::IntegrationTest` in favor of `ActionDispatch::IntegrationTest`.
* Rails 4.0 deprecated `ActionController::PerformanceTest` in favor of `ActionDispatch::PerformanceTest`.
* Rails 4.0 deprecated `ActionController::AbstractRequest` in favor of `ActionDispatch::Request`.
* Rails 4.0 deprecated `ActionController::Request` in favor of `ActionDispatch::Request`.
* Rails 4.0 deprecated `ActionController::AbstractResponse` in favor of `ActionDispatch::Response`.
* Rails 4.0 deprecated `ActionController::Response` in favor of `ActionDispatch::Response`.
* Rails 4.0 deprecated `ActionController::Routing` in favor of `ActionDispatch::Routing`.
#### 4.8 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`.
#### 4.9 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.
#### 4.10 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.
#### 4.11 sprockets-rails
* `assets:precompile:primary` and `assets:precompile:all` have been removed. Use `assets:precompile` instead.
* The `config.assets.compress` option should be changed to `config.assets.js_compressor` like so for instance:
```
config.assets.js_compressor = :uglifier
```
#### 4.12 sass-rails
* `asset-url` with two arguments is deprecated. For example: `asset-url("rails.png", image)` becomes `asset-url("rails.png")`.
### 5 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 the latest 3.2.x version of Rails.
#### 5.1 Gemfile
Make the following changes to your `Gemfile`.
```
gem 'rails', '3.2.18'
group :assets do
gem 'sass-rails', '~> 3.2.6'
gem 'coffee-rails', '~> 3.2.2'
gem 'uglifier', '>= 1.0.3'
end
```
#### 5.2 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
```
#### 5.3 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
```
#### 5.4 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`.
#### 5.5 Active Record
Option `:dependent => :restrict` has been removed from `belongs_to`. If you want to prevent deleting the object if there are any associated objects, you can set `:dependent => :destroy` and return `false` after checking for existence of association from any of the associated object's destroy callbacks.
### 6 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 3.1.12, the last 3.1.x version of Rails.
#### 6.1 Gemfile
Make the following changes to your `Gemfile`.
```
gem 'rails', '3.1.12'
gem 'mysql2'
# Needed for the new asset pipeline
group :assets do
gem 'sass-rails', '~> 3.1.7'
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'
```
#### 6.2 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'
```
#### 6.3 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
```
#### 6.4 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](asset_pipeline.html) 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
```
#### 6.5 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'
```
#### 6.6 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
```
#### 6.7 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
```
$ bin/rake db:sessions:clear
```
#### 6.8 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.
### 反馈
欢迎帮忙改善指南质量。
如发现任何错误，欢迎修正。开始贡献前，可先行阅读[贡献指南：文档](http://edgeguides.rubyonrails.org/contributing_to_ruby_on_rails.html#contributing-to-the-rails-documentation)。
翻译如有错误，深感抱歉，欢迎 [Fork](https://github.com/ruby-china/guides/fork) 修正，或至此处[回报](https://github.com/ruby-china/guides/issues/new)。
文章可能有未完成或过时的内容。请先检查 [Edge Guides](http://edgeguides.rubyonrails.org) 来确定问题在 master 是否已经修掉了。再上 master 补上缺少的文件。内容参考 [Ruby on Rails 指南准则](ruby_on_rails_guides_guidelines.html)来了解行文风格。
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- Ruby on Rails 指南 (651bba1)
- 入门
- Rails 入门
- 模型
- Active Record 基础
- Active Record 数据库迁移
- Active Record 数据验证
- Active Record 回调
- Active Record 关联
- Active Record 查询
- 视图
- Action View 基础
- Rails 布局和视图渲染
- 表单帮助方法
- 控制器
- Action Controller 简介
- Rails 路由全解
- 深入
- Active Support 核心扩展
- Rails 国际化 API
- Action Mailer 基础
- Active Job 基础
- Rails 程序测试指南
- Rails 安全指南
- 调试 Rails 程序
- 设置 Rails 程序
- Rails 命令行
- Rails 缓存简介
- Asset Pipeline
- 在 Rails 中使用 JavaScript
- 引擎入门
- Rails 应用的初始化过程
- Autoloading and Reloading Constants
- 扩展 Rails
- Rails 插件入门
- Rails on Rack
- 个性化Rails生成器与模板
- Rails应用模版
- 贡献 Ruby on Rails
- Contributing to Ruby on Rails
- API Documentation Guidelines
- Ruby on Rails Guides Guidelines
- Ruby on Rails 维护方针
- 发布记
- A Guide for Upgrading Ruby on Rails
- Ruby on Rails 4.2 发布记
- Ruby on Rails 4.1 发布记
- Ruby on Rails 4.0 Release Notes
- Ruby on Rails 3.2 Release Notes
- Ruby on Rails 3.1 Release Notes
- Ruby on Rails 3.0 Release Notes
- Ruby on Rails 2.3 Release Notes
- Ruby on Rails 2.2 Release Notes