Rails3 Beta 2 changes

rails_3_beta2_changes

Action Pack

* Remove metal from Rails3 [YK]
http://github.com/rails/rails/commit/45e60283e733a535d68d499aa20e095c905f43b0

* :only and :except options in the use of rack middlewares [JV] 
http://github.com/rails/rails/commit/9a93844aba44319d3c8487a554124beb00ccc267

  class PostsController < ApplicationController
    use AutheMiddleware, :except => [:index, :show]
  end

* #concat is now deprecated in favor of using <%= %> helpers [YK]

* Block helpers now return Strings, so you can use <%= form_for @foo do |f| %>.
  <% form_for do |f| %> still works with deprecation notices [YK]

* Add a new #mount method on the router that does not anchor the PATH_INFO
  at the end [YK & CL]

* Create a new LookupContext object that is responsible for performantly
  finding a template for a given pattern [JV]

* Removed relative_url_for in favor of respecting SCRIPT_NAME [YK & CL]

* Changed file streaming to use Rack::Sendfile middleware [YK]

* ActionDispatch::Request#content_type returns a String to be compatible with
  Rack::Request. Use #content_mime_type for the Mime::Type instance [YK]

* Updated Prototype to 1.6.1 and Scriptaculous to 1.8.3 [ML] 

* Change the preferred way that URL helpers are included into a class[YK & CL]

    # for all helpers including named routes
    include Rails.application.router.url_helpers

    # for just url_for
    include Rails.application.router.url_for


Active Model

* #new_record? and #destroyed? were removed from ActiveModel::Lint. Use
  persisted? instead. A model is persisted if it's not a new_record? and it was 
  not destroyed? [MG]

* Added validations reflection in ActiveModel::Validations [JV]

    Model.validators
    Model.validators_on(:field)

* #to_key was added to ActiveModel::Lint so we can generate DOM IDs for
  AMo objects with composite keys [MG]


Active Record

* To prefix the table names of all models in a module, define self.table_name_prefix on the module.  #4032 [Andrew White]

* Silenced "SHOW FIELDS" and "SET SQL_AUTO_IS_NULL=0" statements from the MySQL driver to improve log signal to noise ration in development [DHH]


Active Support

* Reduced load time by deferring configuration of classes using
  ActiveSupport::on_load(:component_name) [YK]

* Rename #metaclass to #singleton_class now that ruby-core has decided [JK]

* New assertions assert_blank and assert_present.  #4299 [Juanjo Bazan] 

* Use Object#singleton_class instead of #metaclass. Prefer Ruby's choice.  [Jeremy Kemper]

* JSON backend for YAJL. Preferred if available.  #2666 [Brian Lopez]


Action Mailer

* Added interceptors and observers from Mail [ML]

    ActionMailer::Base.register_interceptor calls Mail.register_interceptor
    ActionMailer::Base.register_observer calls Mail.register_observer

* Whole new API added with tests.  See base.rb for full details.  Old API is deprecated.