rails3.txt

= Modularity
== ActiveSupport
It is now viable to cherry-pick specific elements. All dependencies are explicit. Even better other parts of Rails now explicitly declare the dependencies they have on ActiveSupport. However, for simplicity, Rails 3 ships with all of ActiveSupport still provided. To turn it off, declare +config.active_support.bare = true+ in the configuration file (so, 3.days is not available any more unless the specific module is included).

== ActionController
It is splited into three parts:
* ActionDispatch: includes the dispatcher functionality.
* AbstractController: includes codes that were meant to be reused by non-HTTP controllers. Both ActionController and ActionMailer inherit from it.
* ActionController: the HTTP controller. Every standalone component has benn isolated, and it's possible to start with a stripped-down controller and pull in just the components that are needed. +ActionController::Base+ simply starts with that same stripped-down contrller and pulls everything in.
    module ActionController
      class Base < Metal
        abstract!

        include AbstractController::Callbacks
        include AbstractController::Logger

        include AbstractController::Helpers
        ...
      end
    end
Example of customizing controllers:
    class FasterController < ActionController::Metal
      abstract!

      # Rendering would be pulled in by layouts, but I include it here for clarity
      include ActionController::Rendering
      include ActionController::Layouts

      append_view_path Rails.root.join("app/views")
    end

    class AwesomeController < FasterController
      def index; redner "so_speedy" end
    end

    # in routes
    MyApp.routes.draw { match "/must_be_fast" => "awesome#index" }
+ActioinController::Middleware+, which is middleware with all of the powers of ActionController, allows you to pull in whatever ActionController features you want as needed. Example:
    class MyMiddleware < ActionController::Middleware
      include ActionController::ConditionalGet
      include ...

      def call(env)
        ...
      end
    end

= Performance
A few of the performance optimizations:
* Reducing general controller overhead
* (greatly) Speeding up rendering a collection of partials
* more!

= Plugin API
Even Rails 3 itself is trying to build itself on the core components. (Like ActionPack)

= ActiveModel
* Use ActiveModel::Lint to test a object if it's ActiveModel compliant.
* Two major elements:
  * ActiveModel API
  * ActiveModel Modules

.... TO BE CONTINUE! STAY TUNE!