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Ruby on Rails 2.2 Release Notes

Rails 2.2 delivers several new and improved features. This list covers the major upgrades but doesn't include every little bug fix and change. If you want to see everything, check out thelist of commits in the main Rails repository on GitHub.

Along with Rails, 2.2 marks the launch of theRuby on Rails Guides, the first results of the ongoingRails Guides hackfest. This site will deliver high-quality documentation of the major features of Rails.

1. Infrastructure

Rails 2.2 is a significant release for the infrastructure that keeps Rails humming along and connected to the rest of the world.

1.1. Internationalization

Rails 2.2 supplies an easy system for internationalization (or i18n, for those of you tired of typing).

1.2. Compatibility with Ruby 1.9 and JRuby

Along with thread safety, a lot of work has been done to make Rails work well with JRuby and the upcoming Ruby 1.9. With Ruby 1.9 being a moving target, running edge Rails on edge Ruby is still a hit-or-miss proposition, but Rails is ready to make the transition to Ruby 1.9 when the latter is released.

2. Documentation

The internal documentation of Rails, in the form of code comments, has been improved in numerous places. In addition, theRuby on Rails Guides project is the definitive source for information on major Rails components. In its first official release, the Guides page includes:

All told, the Guides provide tens of thousands of words of guidance for beginning and intermediate Rails developers.

If you want to generate these guides locally, inside your application:

$rakedoc:guides

This will put the guides insideRails.root/doc/guides and you may start surfing straight away by openingRails.root/doc/guides/index.html in your favorite browser.

3. Better integration with HTTP : Out of the box ETag support

Supporting the ETag and last modified timestamp in HTTP headers means that Rails can now send back an empty response if it gets a request for a resource that hasn't been modified lately. This allows you to check whether a response needs to be sent at all.

classArticlesController<ApplicationControllerdefshow_with_respond_to_block@article=Article.find(params[:id])# If the request sends headers that differs from the options provided to stale?, then# the request is indeed stale and the respond_to block is triggered (and the options# to the stale? call is set on the response).## If the request headers match, then the request is fresh and the respond_to block is# not triggered. Instead, the default render will occur, which will check the last-modified# and etag headers and conclude that it only needs to send a "304 Not Modified" instead# of rendering the template.ifstale?(:last_modified=>@article.published_at.utc,:etag=>@article)respond_todo|wants|# normal response processingendendenddefshow_with_implied_render@article=Article.find(params[:id])# Sets the response headers and checks them against the request, if the request is stale# (i.e. no match of either etag or last-modified), then the default render of the template happens.# If the request is fresh, then the default render will return a "304 Not Modified"# instead of rendering the template.fresh_when(:last_modified=>@article.published_at.utc,:etag=>@article)endend

4. Thread Safety

The work done to make Rails thread-safe is rolling out in Rails 2.2. Depending on your web server infrastructure, this means you can handle more requests with fewer copies of Rails in memory, leading to better server performance and higher utilization of multiple cores.

To enable multithreaded dispatching in production mode of your application, add the following line in yourconfig/environments/production.rb:

config.threadsafe!

5. Active Record

There are two big additions to talk about here: transactional migrations and pooled database transactions. There's also a new (and cleaner) syntax for join table conditions, as well as a number of smaller improvements.

5.1. Transactional Migrations

Historically, multiple-step Rails migrations have been a source of trouble. If something went wrong during a migration, everything before the error changed the database and everything after the error wasn't applied. Also, the migration version was stored as having been executed, which means that it couldn't be simply rerun byrake db:migrate:redo after you fix the problem. Transactional migrations change this by wrapping migration steps in a DDL transaction, so that if any of them fail, the entire migration is undone. In Rails 2.2, transactional migrations are supported on PostgreSQL out of the box. The code is extensible to other database types in the future - and IBM has already extended it to support the DB2 adapter.

5.2. Connection Pooling

Connection pooling lets Rails distribute database requests across a pool of database connections that will grow to a maximum size (by default 5, but you can add apool key to yourdatabase.yml to adjust this). This helps remove bottlenecks in applications that support many concurrent users. There's also await_timeout that defaults to 5 seconds before giving up.ActiveRecord::Base.connection_pool gives you direct access to the pool if you need it.

development:adapter:mysqlusername:rootdatabase:sample_developmentpool:10wait_timeout:10

5.3. Hashes for Join Table Conditions

You can now specify conditions on join tables using a hash. This is a big help if you need to query across complex joins.

classPhoto<ActiveRecord::Basebelongs_to:productendclassProduct<ActiveRecord::Basehas_many:photosend# Get all products with copyright-free photos:Product.all(:joins=>:photos,:conditions=>{:photos=>{:copyright=>false}})

5.4. New Dynamic Finders

Two new sets of methods have been added to Active Record's dynamic finders family.

5.4.1.find_last_by_attribute

Thefind_last_by_attribute method is equivalent toModel.last(:conditions => {:attribute => value})

# Get the last user who signed up from LondonUser.find_last_by_city('London')

5.4.2.find_by_attribute!

The new bang! version offind_by_attribute! is equivalent toModel.first(:conditions => {:attribute => value}) || raise ActiveRecord::RecordNotFound Instead of returningnil if it can't find a matching record, this method will raise an exception if it cannot find a match.

# Raise ActiveRecord::RecordNotFound exception if 'Moby' hasn't signed up yet!User.find_by_name!('Moby')

5.5. Associations Respect Private/Protected Scope

Active Record association proxies now respect the scope of methods on the proxied object. Previously (given User has_one :account)@user.account.private_method would call the private method on the associated Account object. That fails in Rails 2.2; if you need this functionality, you should use@user.account.send(:private_method) (or make the method public instead of private or protected). Please note that if you're overridingmethod_missing, you should also overriderespond_to to match the behavior in order for associations to function normally.

5.6. Other Active Record Changes

  • rake db:migrate:redo now accepts an optional VERSION to target that specific migration to redo
  • Setconfig.active_record.timestamped_migrations = false to have migrations with numeric prefix instead of UTC timestamp.
  • Counter cache columns (for associations declared with:counter_cache => true) do not need to be initialized to zero any longer.
  • ActiveRecord::Base.human_name for an internationalization-aware humane translation of model names

6. Action Controller

On the controller side, there are several changes that will help tidy up your routes. There are also some internal changes in the routing engine to lower memory usage on complex applications.

6.1. Shallow Route Nesting

Shallow route nesting provides a solution to the well-known difficulty of using deeply-nested resources. With shallow nesting, you need only supply enough information to uniquely identify the resource that you want to work with.

map.resources:publishers,:shallow=>truedo|publisher|publisher.resources:magazinesdo|magazine|magazine.resources:photosendend

This will enable recognition of (among others) these routes:

/publishers/1           ==> publisher_path(1)/publishers/1/magazines ==> publisher_magazines_path(1)/magazines/2            ==> magazine_path(2)/magazines/2/photos     ==> magazines_photos_path(2)/photos/3               ==> photo_path(3)

6.2. Method Arrays for Member or Collection Routes

You can now supply an array of methods for new member or collection routes. This removes the annoyance of having to define a route as accepting any verb as soon as you need it to handle more than one. With Rails 2.2, this is a legitimate route declaration:

map.resources:photos,:collection=>{:search=>[:get,:post]}

6.3. Resources With Specific Actions

By default, when you usemap.resources to create a route, Rails generates routes for seven default actions (index, show, create, new, edit, update, and destroy). But each of these routes takes up memory in your application, and causes Rails to generate additional routing logic. Now you can use the:only and:except options to fine-tune the routes that Rails will generate for resources. You can supply a single action, an array of actions, or the special:all or:none options. These options are inherited by nested resources.

map.resources:photos,:only=>[:index,:show]map.resources:products,:except=>:destroy

6.4. Other Action Controller Changes

  • You can now easilyshow a custom error page for exceptions raised while routing a request.
  • The HTTP Accept header is disabled by default now. You should prefer the use of formatted URLs (such as/customers/1.xml) to indicate the format that you want. If you need the Accept headers, you can turn them back on withconfig.action_controller.use_accept_header = true.
  • Benchmarking numbers are now reported in milliseconds rather than tiny fractions of seconds
  • Rails now supports HTTP-only cookies (and uses them for sessions), which help mitigate some cross-site scripting risks in newer browsers.
  • redirect_to now fully supports URI schemes (so, for example, you can redirect to a svn`ssh: URI).
  • render now supports a:js option to render plain vanilla JavaScript with the right MIME type.
  • Request forgery protection has been tightened up to apply to HTML-formatted content requests only.
  • Polymorphic URLs behave more sensibly if a passed parameter is nil. For example, callingpolymorphic_path([@project, @date, @area]) with a nil date will give youproject_area_path.

7. Action View

  • javascript_include_tag andstylesheet_link_tag support a new:recursive option to be used along with:all, so that you can load an entire tree of files with a single line of code.
  • The included Prototype JavaScript library has been upgraded to version 1.6.0.3.
  • RJS#page.reload to reload the browser's current location via JavaScript
  • Theatom_feed helper now takes an:instruct option to let you insert XML processing instructions.

8. Action Mailer

Action Mailer now supports mailer layouts. You can make your HTML emails as pretty as your in-browser views by supplying an appropriately-named layout - for example, theCustomerMailer class expects to uselayouts/customer_mailer.html.erb.

Action Mailer now offers built-in support for GMail's SMTP servers, by turning on STARTTLS automatically. This requires Ruby 1.8.7 to be installed.

9. Active Support

Active Support now offers built-in memoization for Rails applications, theeach_with_object method, prefix support on delegates, and various other new utility methods.

9.1. Memoization

Memoization is a pattern of initializing a method once and then stashing its value away for repeat use. You've probably used this pattern in your own applications:

deffull_name@full_name||="#{first_name}#{last_name}"end

Memoization lets you handle this task in a declarative fashion:

extendActiveSupport::Memoizabledeffull_name"#{first_name}#{last_name}"endmemoize:full_name

Other features of memoization includeunmemoize,unmemoize_all, andmemoize_all to turn memoization on or off.

9.2. each_with_object

Theeach_with_object method provides an alternative toinject, using a method backported from Ruby 1.9. It iterates over a collection, passing the current element and the memo into the block.

%w(foo bar).each_with_object({}){|str,hsh|hsh[str]=str.upcase}# => {'foo' => 'FOO', 'bar' => 'BAR'}

Lead Contributor:Adam Keys

9.3. Delegates With Prefixes

If you delegate behavior from one class to another, you can now specify a prefix that will be used to identify the delegated methods. For example:

classVendor<ActiveRecord::Basehas_one:accountdelegate:email,:password,:to=>:account,:prefix=>trueend

This will produce delegated methodsvendor#account_email andvendor#account_password. You can also specify a custom prefix:

classVendor<ActiveRecord::Basehas_one:accountdelegate:email,:password,:to=>:account,:prefix=>:ownerend

This will produce delegated methodsvendor#owner_email andvendor#owner_password.

Lead Contributor:Daniel Schierbeck

9.4. Other Active Support Changes

  • Extensive updates toActiveSupport::Multibyte, including Ruby 1.9 compatibility fixes.
  • The addition ofActiveSupport::Rescuable allows any class to mix in therescue_from syntax.
  • past?,today? andfuture? forDate andTime classes to facilitate date/time comparisons.
  • Array#second throughArray#fifth as aliases forArray#[1] throughArray#[4]
  • Enumerable#many? to encapsulatecollection.size > 1
  • Inflector#parameterize produces a URL-ready version of its input, for use into_param.
  • Time#advance recognizes fractional days and weeks, so you can do1.7.weeks.ago,1.5.hours.since, and so on.
  • The included TzInfo library has been upgraded to version 0.3.12.
  • ActiveSupport::StringInquirer gives you a pretty way to test for equality in strings:ActiveSupport::StringInquirer.new("abc").abc? => true

10. Railties

In Railties (the core code of Rails itself) the biggest changes are in theconfig.gems mechanism.

10.1. config.gems

To avoid deployment issues and make Rails applications more self-contained, it's possible to place copies of all of the gems that your Rails application requires in/vendor/gems. This capability first appeared in Rails 2.1, but it's much more flexible and robust in Rails 2.2, handling complicated dependencies between gems. Gem management in Rails includes these commands:

  • config.gem _gem_name_ in yourconfig/environment.rb file
  • rake gems to list all configured gems, as well as whether they (and their dependencies) are installed, frozen, or framework (framework gems are those loaded by Rails before the gem dependency code is executed; such gems cannot be frozen)
  • rake gems:install to install missing gems to the computer
  • rake gems:unpack to place a copy of the required gems into/vendor/gems
  • rake gems:unpack:dependencies to get copies of the required gems and their dependencies into/vendor/gems
  • rake gems:build to build any missing native extensions
  • rake gems:refresh_specs to bring vendored gems created with Rails 2.1 into alignment with the Rails 2.2 way of storing them

You can unpack or install a single gem by specifyingGEM=_gem_name_ on the command line.

10.2. Other Railties Changes

  • If you're a fan of theThin web server, you'll be happy to know thatscript/server now supports Thin directly.
  • script/plugin install &lt;plugin&gt; -r &lt;revision&gt; now works with git-based as well as svn-based plugins.
  • script/console now supports a--debugger option
  • Instructions for setting up a continuous integration server to build Rails itself are included in the Rails source
  • rake notes:custom ANNOTATION=MYFLAG lets you list out custom annotations.
  • WrappedRails.env inStringInquirer so you can doRails.env.development?
  • To eliminate deprecation warnings and properly handle gem dependencies, Rails now requires rubygems 1.3.1 or higher.

11. Deprecated

A few pieces of older code are deprecated in this release:

  • Rails::SecretKeyGenerator has been replaced byActiveSupport::SecureRandom
  • render_component is deprecated. There's arender_components plugin available if you need this functionality.

  • Implicit local assignments when rendering partials has been deprecated.

    defpartial_with_implicit_local_assignment@customer=Customer.new("Marcel")render:partial=>"customer"end

    Previously the above code made available a local variable calledcustomer inside the partial 'customer'. You should explicitly pass all the variables via :locals hash now.

  • country_select has been removed. See thedeprecation page for more information and a plugin replacement.

  • ActiveRecord::Base.allow_concurrency no longer has any effect.

  • ActiveRecord::Errors.default_error_messages has been deprecated in favor ofI18n.translate('activerecord.errors.messages')

  • The%s and%d interpolation syntax for internationalization is deprecated.

  • String#chars has been deprecated in favor ofString#mb_chars.

  • Durations of fractional months or fractional years are deprecated. Use Ruby's coreDate andTime class arithmetic instead.

  • Request#relative_url_root is deprecated. UseActionController::Base.relative_url_root instead.

12. Credits

Release notes compiled byMike Gunderloy

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