What's new and great in Rails 3 - Matt Gauger - Milwaukee Ruby Users Group December 2010

What’s new and great in

Rails 3

Don’t worry!

All the links Text
shown will be
presented at the end of the
slides and on my blog.

There’s a lot to talk
about, so

I wanted to do
something different than
list the changes in Rails 3

Allow me to introduce
you to someone.

What's new and great in Rails 3 - Matt Gauger - Milwaukee Ruby Users Group December 2010

“Robin would very much like to be a
kick-ass web developer, but has a hard
time keeping up with the buzzwords.”
-- Flickr description

where they make state-of-the-art
TODO list web applications
(and ﬁght crime)

Wants the team to
use Rails 3.

Because he heard it
is the new hotness.

Batman tries to stay hip
with the “web stuff”

Robin is already fairly
familiar with Rails

In this case, he’s going to
be starting from scratch

While it is possible to
upgrade from Rails 2.x to
Rails 3, we’re not going to.

This is merely a learning
exercise, so we’re skipping
the BDD/TDD for now, too.

Robin keeps up with
a few Rails blogs,

And he’s read that rvm
is what everyone is using

rvm is a way to install and
use different versions of
Ruby on the same machine

Robin uses Homebrew
on his Mac, so he types:

Sidenote:
My recommendation would be to start
with Cinderella if you’re on a Mac

• mysql, postgres, redis, memcached and
mongodb
•ruby (1.8.7) with rails and sinatra via
rvm gemsets. (& install Ruby 1.9 with rvm)
•python (2.7) with pip.
•node.js (0.2.0) with npm.
•erlang (R13B04) environment.
... and brew, and probably a lot more by
now.

$ rvm install 1.9.2
$ rvm use 1.9.2

$ rvm list

rvm rubies

ruby-1.8.7-p248 [ x86_64 ]
=> ruby-1.9.2-p0 [ x86_64 ]

$ ruby -v
ruby 1.9.2p0 (2010-08-18 revision
29036) [x86_64-darwin10.4.1]

So now Robin is
rolling on Ruby 1.9.2

A gemset is a collection of
gems, in this case that we’re
associating with a project

Robin knows this comes
in later, when he starts
using bundler in his app

$ rvm gemset create totodo
$ rvm ruby-1.9.2-p0@totodo

Now any gems he installs
will be on Ruby 1.9.2

And more importantly,
will be kept with his app.

He creates a new app called
totodo (it’s a todo list!)

# Create a new Rails 3 app:
$ rails new totodo
$ cd totodo/

And grabs gems that
Rails needs with Bundler

# Use Bundler to install gems:
$ bundle install

In Rails 2, Robin
would have to do this:

# Edit environment.rb:
config.gem "haml"
config.gem "sass"

# Then do
$ rake gems:install

# Edit the Gemfile:
source "http://rubygems.org"

gem "haml"
gem "sass"

# Then run:
$ bundle install

We can also use
groups for gems:

# Gemfile:
source "http://rubygems.org"

gem "haml"
gem "sass"

group :test,:development do
gem "webrat"
gem "rspec"
end

# Then go run:
$ bundle

Now webrat and rspec will
be installed and used, but
only in the environments listed

Moving on, we set
up git and heroku

# Set up git repo:
$ git init .
$ git add *
$ git commit -m “Initial commit of
bare Rails 3 project.”

# Create a new Heroku app:
$ heroku create
$ git push heroku master

Robin is all set to
develop

He’s is looking at the
ﬁles in his newly
created project,

and noticing some
differences

conﬁg/application.rb
(replaces conﬁg/environment.rb)

require File.expand_path('../boot', __FILE__)

require 'rails/all'

# If you have a Gemfile, require the gems listed there, including any gems
# you've limited to :test, :development, or :production.
Bundler.require(:default, Rails.env) if defined?(Bundler)

module Totodo
class Application < Rails::Application
# [With a lot of comments cleaned up]

# Configure generators values.
config.generators do |g|
g.orm :active_record
g.template_engine :haml
g.test_framework :rspec, :fixture => true
end

# Configure the default encoding used in templates for Ruby 1.9.
config.encoding = "utf-8"

# Configure sensitive parameters which will be filtered from the log file.
config.filter_parameters += [:password]
end
end

# Robin is going to use haml and rspec:

# Configure generators values.
config.generators do |g|
g.orm :active_record
g.template_engine :haml
g.test_framework :rspec
end

Robin needs a data model
for what he’s storing

What makes up a
TODO list item?

•ID
•Title (Text)
•Due Date (Datetime)
•Is it done? (Boolean)

Robin wants to use
$ script/generate
which he comfortable with

But there isn’t a
script/generate in Rails 3

# Inside his totodo project folder:
$ ls -al script/
total 8
drwxr-xr-x 3 robin staff 102 Dec 20 01:53 .
drwxr-xr-x 21 robin staff 714 Dec 20 01:55 ..
-rwxr-xr-x 1 robin staff 295 Dec 20 01:53 rails

Instead, everything goes
through the rails script

# Remember doing these commands?
$ script/generate something
$ script/server
$ script/console

# Replaced with:

$ rails generate something
$ rails g something #shorter form

$ rails server
$ rails s # shorter form

$ rails console

What Robin wants is
a scaffold

Again, he’s just learning
Rails 3 here, so a
scaffold will be ﬁne.

$ rails generate scaffold Todo title:string
due_date:datetime done:boolean

$ rails generate scaffold Todo title:string due_date:datetime done:boolean
invoke active_record
create db/migrate/20101220080933_create_todos.rb
create app/models/todo.rb
invoke test_unit
create test/unit/todo_test.rb
create test/fixtures/todos.yml
route resources :todos
invoke scaffold_controller
create app/controllers/todos_controller.rb
invoke erb
create app/views/todos
create app/views/todos/index.html.erb
create app/views/todos/edit.html.erb
create app/views/todos/show.html.erb
create app/views/todos/new.html.erb
create app/views/todos/_form.html.erb

[and lots more output than this]

That’s a lot of
generated ﬁles

Robin wants to know
whether migrations are
different in Rails 3

db/migrate/20101220080933_create_todos.rb

class CreateTodos < ActiveRecord::Migration
def self.up
create_table :todos do |t|
t.string :title
t.datetime :due_date
t.boolean :done

t.timestamps
end
end

def self.down
drop_table :todos
end
end

That’s very similar to
what Robin is used to.

$ rake db:migrate
(in /Users/robin/Projects/totodo)
== CreateTodos: migrating ==================================
-- create_table(:todos)
-> 0.0019s
== CreateTodos: migrated (0.0020s) =========================

Now, Robin wants to hook up
the routes to his new controller

He’s read that routes in
Rails 3 are different,

He’s pleased to ﬁnd
that they’re simple:

# in config/routes.rb our scaffold placed:

Totodo::Application.routes.draw do
resources :todos

end

Robin deletes the
public/index.html ﬁle and maps
the root path:

root :to => 'todos#index'
resources :todos

end

And runs his dev server with
that nifty `rails s` command

Robin wants validations
on his model

A ToDo list item
should have a title

The syntax has
changed a little

class Todo < ActiveRecord::Base
validates :title, :presence => true
end

Robin has a very,
very basic app started

And a long way to
go with Rails 3

Robin has a little bit of
time during his lunch break

So he reads up on
the Merb project

2006:
The Merb project was
started

At its start, Merb just
serves ERb templates
from Mongrel

December 2008:
The Rails team announces
RoR and Merb will merge

Rails 3 is the result of
merging Merb and RoR

And represents a
signiﬁcant rewrite of
most of Rails

Robin has stumbled
onto a blog post by

Summarizing the
Merb+RoR merger
back in 2008

Rails will become
more modular

Rails will have better
performance

Rails 3 will have a
deﬁned API, and a
test suite for that API

Rails will allow things like
DataMapper or Sequel
to be ﬁrst-class ORMs

Rails 3 will continue
to embrace Rack

Reinvigorated, Robin
jumps back into dev

As he begins to modify
his controller, he runs into

Arel provides an
SQL abstraction

@users = User.find(:all, :conditions => {:approved => true})

@users = User.where(:approved => true)

The Rails 2.x-style .ﬁnd()
method queries the DB
immediately and returns an
array

The Arel-style .where()
method returns an
ActiveRecord::Relation

What can we do with
an ActiveRelation?

Add additional
parameters to the query


# If a params[:order] was passed in,
# add that condition to the query:
@users = @users.order(params[:order])

@users.each do |u|
...
end


# If a params[:order] was passed in,
# add that condition to the query:
@users = @users.order(params[:order])

@users.each do |u| # Query runs here!
...
end

We can even chain the last
page of code together:

User.where(:approved => true).order(params[:order])

# Rails 2:
class User < ActiveRecord::Base
named_scope :approved, :conditions => {:approved => true}
end

# Rails 3:
class User < ActiveRecord::Base
scope :approved, where(:approved => true)
end

There’s much, much more to Arel.
Read the documentation.

Next up, Robin discovers
that he can match any
Rack app to a route

Totodo::Application.routes do
match "/home", :to => HomeApp
end

In fact, this is a lot like
the routes we saw earlier

root :to => 'todos#index'
match "/home", :to => HomeApp
end

'todos#index'
here is really a full ﬂedged
Rack application, too.

Routes are namespaced
inside your app.

# Instead of:

ActionController::Routing::Routes.draw do |map|
map.resources :todos
end

# You do:

Totodo::Application.routes do
resources :todos
end

The i18n gem brings in better
i18n support, but Robin isn’t
going to get into that right now.

How has our
Controller changed?

A simpliﬁed version of
what our scaffold
created would be:

class TodosController < ApplicationController
respond_to :html, :xml, :js

# GET /todos
# GET /todos.xml
def index
respond_with(@todos = Todo.all)
end
end

As you can see, respond_to
deﬁnes the formats the
Controller responds to

And responds_with is
the data to send back

Our scaffold has already
created the methods for
our Todos controller

Robin pushes the
app to Heroku

$ git push heroku master
[... lots of output ...]
-----> Launching... done
http://deep-mountain-360.heroku.com/
deployed to Heroku

To git@heroku.com:deep-mountain-360.git
* [new branch] master -> master

Where can Robin go
to learn more?

Robin can work through the
Rails Tutorial book for Rails 3:
http://railstutorial.org/book

Which is a great resource.
Highly recommended!

Robin is now equipped
to ﬁght crime, write
TODO lists, and learn
more about Rails 3!

His boss wants to give
him a little congrats

See me after for free
Github stickers :-)

Media used:
http://www.flickr.com/photos/geirarne/43102913/
(CC Attribution-NonCommercial-ShareAlike 2.0)

http://www.flickr.com/photos/redraspus/2883658175
(CC Attribution-NonCommercial-ShareAlike 2.0)

http://www.flickr.com/photos/patolucas/2862975260/
(CC Attribution-ShareAlike 2.0 Generic)

Links:
https://github.com/atmos/cinderella

http://rvm.beginrescueend.com/

http://yehudakatz.com/2008/12/23/rails-and-merb-merge/

http://railsforzombies.org
http://railstutorial.org/book
http://rubyonrails.org/screencasts/rails3/
https://github.com/brynary/arel

What's new and great in Rails 3 - Matt Gauger - Milwaukee Ruby Users Group December 2010

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