actionpack-rack-upgrade

= Action Pack -- On rails from request to response

Action Pack splits the response to a web request into a controller part (performing the logic) and a view part (rendering a template). This two-step approach is known as an action, which will normally create, read, update, or delete (CRUD for short) some sort of model part (often backed by a database) before choosing either to render a template or redirecting to another action.

Action Pack implements these actions as public methods on Action Controllers and uses Action Views to implement the template rendering. Action Controllers are then responsible for handling all the actions relating to a certain part of an application. This grouping usually consists of actions for lists and for CRUDs revolving around a single (or a few) model objects. So ContactsController would be responsible for listing contacts, creating, deleting, and updating contacts. A WeblogController could be responsible for both posts and comments.

Action View templates are written using embedded Ruby in tags mingled in with the HTML. To avoid cluttering the templates with code, a bunch of helper classes provide common behavior for forms, dates, and strings. And it's easy to add specific helpers to keep the separation as the application evolves.

Note: Some of the features, such as scaffolding and form building, are tied to ActiveRecord[http://activerecord.rubyonrails.org] (an object-relational mapping package), but that doesn't mean that Action Pack depends on Active Record. Action Pack is an independent package that can be used with any sort of backend (Instiki[http://www.instiki.org], which is based on an older version of Action Pack, used Madeleine for example). Read more about the role Action Pack can play when used together with Active Record on http://www.rubyonrails.org.

A short rundown of the major features:

• Actions grouped in controller as methods instead of separate command objects and can therefore share helper methods

  CustomersController < ActionController::Base def show @customer = find_customer end

  def update
    @customer = find_customer
    @customer.attributes = params[:customer]
    @customer.save ? 
      redirect_to(:action => "show") :
      render(:action => "edit")
  end
  
  private
    def find_customer() Customer.find(params[:id]) end
  

  end

  {Learn more}[link:classes/ActionController/Base.html]

• Embedded Ruby for templates (no new "easy" template language)

  <% for post in @posts %> Title: <%= post.title %> <% end %>

  All post titles: <%= @posts.collect{ |p| p.title }.join ", " %>

  <% unless @person.is_client? %> Not for clients to see... <% end %>

  {Learn more}[link:classes/ActionView.html]

• Builder-based templates (great for XML content, like RSS)

  xml.rss("version" => "2.0") do xml.channel do xml.title(@feed_title) xml.link(@url) xml.description "Basecamp: Recent items" xml.language "en-us" xml.ttl "40"

    for item in @recent_items
      xml.item do
        xml.title(item_title(item))
        xml.description(item_description(item))
        xml.pubDate(item_pubDate(item))
        xml.guid(@recent_items.url(item))
        xml.link(@recent_items.url(item))
      end
    end
  end
  

  end

  {Learn more}[link:classes/ActionView/Base.html]

• Filters for pre and post processing of the response (as methods, procs, and classes)

  class WeblogController < ActionController::Base before_filter :authenticate, :cache, :audit after_filter { |c| c.response.body = Gzip::compress(c.response.body) } after_filter LocalizeFilter

  def index
    # Before this action is run, the user will be authenticated, the cache
    # will be examined to see if a valid copy of the results already
    # exists, and the action will be logged for auditing.
    
    # After this action has run, the output will first be localized then 
    # compressed to minimize bandwidth usage
  end
  
  private
    def authenticate
      # Implement the filter with full access to both request and response
    end
  

  end

  {Learn more}[link:classes/ActionController/Filters/ClassMethods.html]

• Helpers for forms, dates, action links, and text

  <%= text_field "post", "title", "size" => 30 %> <%= html_date_select(Date.today) %> <%= link_to "New post", :controller => "post", :action => "new" %> <%= truncate(post.title, :length => 25) %>

  {Learn more}[link:classes/ActionView/Helpers.html]

• Layout sharing for template reuse (think simple version of Struts Tiles[http://jakarta.apache.org/struts/userGuide/dev_tiles.html])

  class WeblogController < ActionController::Base layout "weblog_layout"

  def hello_world
  end
  

  end

  Layout file (called weblog_layout): <%= yield %>

  Template for hello_world action:

  Hello world

  Result of running hello_world action:

  Hello world

  {Learn more}[link:classes/ActionController/Layout/ClassMethods.html]

• Routing makes pretty urls incredibly easy

  map.connect 'clients/:client_name/:project_name/:controller/:action'

  Accessing /clients/37signals/basecamp/project/dash calls ProjectController#dash with { "client_name" => "37signals", "project_name" => "basecamp" }.

  From that URL you can redirect providing new parameters in a number of ways:

  redirect_to :action => "edit"

  /clients/37signals/basecamp/project/edit

  redirect_to :client_name => "nextangle", :project_name => "rails"

  /clients/nextangle/rails/project/dash

  {Learn more}[link:classes/ActionController/Base.html]

• JavaScript and Ajax integration

  link_to_function "Greeting", "alert('Hello world!')" link_to_remote "Delete this post", :update => "posts", :url => { :action => "destroy", :id => post.id }

  {Learn more}[link:classes/ActionView/Helpers/JavaScriptHelper.html]

• Easy testing of both controller and rendered template through ActionController::TestCase

  class LoginControllerTest < ActionController::TestCase def test_failing_authenticate process :authenticate, :user_name => "nop", :password => "" assert flash.has_key?(:alert) assert_redirected_to :action => "index" end end

  {Learn more}[link:classes/ActionController/TestCase.html]

• Automated benchmarking and integrated logging

  Processing WeblogController#index (for 127.0.0.1 at Fri May 28 00:41:55) Parameters: {"action"=>"index", "controller"=>"weblog"} Rendering weblog/index (200 OK) Completed in 0.029281 (34 reqs/sec)

  If Active Record is used as the model, you'll have the database debugging as well:

  Processing PostsController#create (for 127.0.0.1 at Sat Jun 19 14:04:23) Params: {"controller"=>"posts", "action"=>"create", "post"=>{"title"=>"this is good"} } SQL (0.000627) INSERT INTO posts (title) VALUES('this is good') Redirected to http://example.com/posts/5 Completed in 0.221764 (4 reqs/sec) | DB: 0.059920 (27%)

  You specify a logger through a class method, such as:

  ActionController::Base.logger = Logger.new("Application Log") ActionController::Base.logger = Log4r::Logger.new("Application Log")

• Caching at three levels of granularity (page, action, fragment)

  class WeblogController < ActionController::Base caches_page :show caches_action :account

  def show
    # the output of the method will be cached as 
    # ActionController::Base.page_cache_directory + "/weblog/show/n.html"
    # and the web server will pick it up without even hitting Rails
  end
  
  def account
    # the output of the method will be cached in the fragment store
    # but Rails is hit to retrieve it, so filters are run
  end
  
  def update
    List.update(params[:list][:id], params[:list])
    expire_page   :action => "show", :id => params[:list][:id]
    expire_action :action => "account"
    redirect_to   :action => "show", :id => params[:list][:id]
  end
  

  end

  {Learn more}[link:classes/ActionController/Caching.html]

• Powerful debugging mechanism for local requests

  All exceptions raised on actions performed on the request of a local user will be presented with a tailored debugging screen that includes exception message, stack trace, request parameters, session contents, and the half-finished response.

  {Learn more}[link:classes/ActionController/Rescue.html]

• Scaffolding for Active Record model objects

  class AccountController < ActionController::Base scaffold :account end

  The AccountController now has the full CRUD range of actions and default templates: list, show, destroy, new, create, edit, update

  {Learn more}[link:classes/ActionController/Scaffolding/ClassMethods.html]

• Form building for Active Record model objects

  The post object has a title (varchar), content (text), and written_on (date)

  <%= form "post" %>

  ...will generate something like (the selects will have more options, of course):

  Title:
  

  Content:
  <%= @post.title %>

  Written on:
  18 July 2004

  <input type="submit" value="Create">
  

  This form generates a params[:post] array that can be used directly in a save action:

  class WeblogController < ActionController::Base def create post = Post.create(params[:post]) redirect_to :action => "show", :id => post.id end end

  {Learn more}[link:classes/ActionView/Helpers/ActiveRecordHelper.html]

• Runs on top of WEBrick, Mongrel, CGI, FCGI, and mod_ruby

== Simple example (from outside of Rails)

This example will implement a simple weblog system using inline templates and an Active Record model. So let's build that WeblogController with just a few methods:

require 'action_controller' require 'post'

class WeblogController < ActionController::Base layout "weblog/layout"

def index
  @posts = Post.find(:all)
end

def show
  @post = Post.find(params[:id])
end

def new
  @post = Post.new
end

def create
  @post = Post.create(params[:post])
  redirect_to :action => "show", :id => @post.id
end

end

WeblogController::Base.view_paths = [ File.dirname(FILE) ] WeblogController.process_cgi if $0 == FILE

The last two lines are responsible for telling ActionController where the template files are located and actually running the controller on a new request from the web-server (like to be Apache).

And the templates look like this:

weblog/layout.html.erb: <%= yield %>

weblog/index.html.erb: <% for post in @posts %>

<%= link_to(post.title, :action => "show", :id => post.id) %>

<% end %>

weblog/show.html.erb:

<%= @post.title %>
<%= @post.content %>

weblog/new.html.erb: <%= form "post" %>

This simple setup will list all the posts in the system on the index page, which is called by accessing /weblog/. It uses the form builder for the Active Record model to make the new screen, which in turn hands everything over to the create action (that's the default target for the form builder when given a new model). After creating the post, it'll redirect to the show page using an URL such as /weblog/5 (where 5 is the id of the post).

== Download

The latest version of Action Pack can be found at

• http://rubyforge.org/project/showfiles.php?group_id=249

Documentation can be found at

• http://api.rubyonrails.com

== Installation

You can install Action Pack with the following command.

% [sudo] ruby install.rb

from its distribution directory.

== License

Action Pack is released under the MIT license.

== Support

The Action Pack homepage is http://www.rubyonrails.org. You can find the Action Pack RubyForge page at http://rubyforge.org/projects/actionpack. And as Jim from Rake says:

Feel free to submit commits or feature requests. If you send a patch, remember to update the corresponding unit tests. If fact, I prefer new feature to be submitted in the form of new unit tests.