RubyConf 2005: Part Six
There were two final day workshops featured at RubyConf. Naturally, I wanted to attend both.
- Hands-on Rails with DHH
- Continuations Demystified with Jim Weirich and Chad Fowler
Although I had originally decided to go to the Continuations workshop, DHH announced that he would be showing the new features in Rails 1.0.
Rails 1.0 addresses several problems with previous releases. We shall have to see how well these actually work when put into practice.
db/schema.rb
Finally, we can specify the DB schema in ruby. No more messing about with DB interfaces. Note it does not cater for foreign keys, only indexes. It does allow constraints to be specified.
ActiveRecord::Schema.define() do
create_table "comments", :force => true do |t|
t.column "body", :text
t.column "heading", :string, :limit => 45, :default => "Moo", :null => false
t.column "post_id", :integer
t.column "author_id", :integer
end
create_table "posts", :force => true do |t|
t.column "name", :string, :size => 45, :null => false
end
create_table "authors", :force => true do |t|
t.column "name", :string, :null => false
end
create_table, :id => false do |t|
t.column "post_id", :integer
t.column "comment_id", :integer
end
add_index "posts", "name"
end
There are a couple of rake tasks which allow you to fetch and dump your DB schema from the DB. These are highly destructive.
rake db_schema_dump
will fetch the DB schema from the DB and overwrite your db/schema.rb with no warning
rake db_schema_import
will overwrite your DB with db/schema.rb and drop all your existing tables and data. This will wipe out your existing data without warning. There is also no transaction support. If your import task fails for any reason, then your DB is in an unknown state. Most likely you no longer have any tables.
Migrations
script/generate migration add_comment_author
will create db/migrate/1_add_comment_author.rb
This allows you to set up a series of events to alter your DB (either just data or schema, or both). It is possible to migrate up and down.
class AddCommentAuthor < ActiveRecord::Migration
def self.up
add_column :posts, :author_name, :string
Post.find(:all).each { |post| post.author_name = "X" }
end
def self.down
remove_column :posts, :author_name
end
end
Rails::Initializer
Whenever a new version of Rails was released, our scripts, environment.rb, etc. of existing applications were not updated. This is being addressed by Rails::Initializer. Now most files which are generated by Rails are stubs pointing into the gems.
script/* are now calling the gems eg.
script/server
#!/usr/bin/ruby1.8
require File.dirname(__FILE__) + '/../config/boot'
require 'commands/server'
environment.rb has been reconfigured: (after removing the comments, it looks like this)
require File.join(File.dirname(__FILE__), 'boot')
Rails::Initializer.run do |config|
end
boot.rb is a bootstrapper to set load paths.
Session storage in the DB is now improved. Intended to be used with first setting up the rails project. Add a configuration option to environment.rb:
# Use the database for sessions instead of the file system
# (create the session table with 'rake create_sessions_table')
config.action_controller.session_store = :active_record_store
then run
rake create_sessions_table
DHH points out that all this is, is a nicer interface to older calls. So all existing environment.rbs should still work. We'll see how abackwardly compatible it actually is.
Rake
The Rakefile has been cut down and modularized. You can add new tasks to lib/tasks
Improved FCGI support
Inside script/process there are three hopefully useful files.
- spawner - this will spawn your FCGI processes
- reaper - this will reload, restart, kill you FCGI processes
- spinner - this will continually call spawner. Not intended for use unless necessary.
haproxy can be used to trick Apache into thinking there is only one fcgi process.
SwitchTower
switchtower --apply-to myrails_app
will create the files:
- config/deploy.rb
- lib/tasks/switchtower.rake
This allows you to write any release things into switchtower.rake eg. hooks into reaper or migration. See manuals.rubyonrails.com for more details
Plugins
Plugins allow you to extend Rails. For example, to add acts_as_something to your AR objects, you would create the directory:
/vendor/plugins/acts_as_something/lib
- init.rb - is called in environment.rb
- acts_as_taggable.rb - contains your class
Prototype 1.4 and Scriptaculous 1.5
Ajax has been improved to allow you to access Ruby objects in Javascript.
Binding Gems and Edge
In previous versions of Rails, we could use any set of gems by explicitly requiring them. Now that the scripts are stubs pointing at the gems, there is a new mechanism to set the rails version you want to use.
rake freeze_gems
This will copy the current rails gems into vendor/
rake unfreeze_rails
This will remove the gems from vendor/
rake freeze_edge
This will pull the latest SVN Edge Rails in to vendor/.
Per-action Session Management
Sessions are accessed whenever someone access the site, whether or not it is necessary. If you are using DB sessions, then there is additional unnecessary overhead. Now we can specify actions which do not need to access sessions information.
class WeblogController < ApplicationController
session :off # no sessions added for any actions
session :off, :only => :feed # sessions off for feed
end
DHH announced that Rails Core would be releasing the release candidate on Sunday afternoon. I believe it is now available as 0.14.0.
