Ruby on Rails For Java
Programmers
Rob Sanheim
www.robsanheim.com
www.seekingalpha.com
www.ajaxian.com

(Briefly) About Me

Why Rails?

Because its fun.

Because it will
make you a better
programmer.

“Learn at least one new [programming] language
every year. Different languages solve the same
problems in different ways. By learning several
different approaches, you can help broaden your
thinking and avoid getting stuck in a rut.”
- David Thomas and Andy Hunt

Because you might
just be able to get
paid for it.

What is Ruby?
• Fully Object Oriented
• Interpreted
• Simple,Yet Powerful
• Open Source
• Born in Japan in 1995
• Yukihiro Matsumoto (“Matz”)

Power
• Closures (aka Blocks)
• Modules
• Reflection
• Open Classes

Typing
• Strong
• Dynamic
• “Duck”

Lets see some code

HelloWorld

Reading a file

Reading a file - Ruby

Collections

Reflection

Ruby on Rails
• David Heinemeier Hansson (DHH)
• Began via Basecamp in mid 2003
• Released July 2004
• Full Stack MVC Web Framework
• Easy database-based web apps

Accolades
• 2006 Jolt award - Web Dev Tool
• Featured in BusinessWeek, Wired
• DHH “Best Hacker” award from Google

Converts
• Dave Thomas
• Bruce Tate
• Stuart Halloway
• Justin Gehtland
• David Geary
• James Duncan Davidson

“Rails is the most well thought-out
web development framework I’ve ever
used. And that’s in a decade of doing
web applications for a living. I’ve built
my own frameworks, helped develop
the Servlet API, and have created more
than a few web servers from scratch.
Nobody has done it like this before.”
-James Duncan Davidson, Creator of
Tomcat and Ant

Platform
• MySQL, PostgreSQL, SQLite, Oracle,
SQL Server, DB2, or Firebird
• develop anywhere
• Apache or LightTPD + FastCGI for
production

* Done via intelligent
reflection and
metaprogramming
* Emphasis on writing code
to get stuff done - avoid
boilerplate
* Scaffolding handles left
over boilerplate
DRY - Don’t
Repeat Yourself

NO XML!
Intelligent Defaults
Only explicitly configure
when necessary
Convention over
Configuration

ActiveRecord
An object that wraps a row in a database
table or view, encapsulates the database
access, and adds domain logic on that data.

Controller and
View
• ActionPack maps URLs to controller
• View handled via Ruby in HTML (RHTML) or builders
• Ajax provided via Prototype and RJS

from: http://www.slash7.com/articles/2005/02/22/mvc-the-most-vexing-conundrum

Lets see some code

create table orders (
id int not null auto_increment,
name varchar(100) not null,
email varchar(255) not null,
address text not null,
pay_type char(10) not null,
shipped_at
datetime null,
primary key (id)
);

class Order < ActiveRecord::Base
end

order = Order.new
order.name = “Rob”
order.email = “rob@yahoo.com”
order.address = “123 1st St”
order.save

an_order = Order.find(24)
robs_order = Order.find(:first, :conditions => "name = 'Rob'")
rob_count = Order.count(:all, :conditions => “name = ‘Rob’”)
robs_order = Order.find_by_name(“Rob”)
more_orders = Order.find_all_by_name_and_pay_type(name, type)
Order.delete(24)
robs_order.destroy

create table order_lines (
id int not null auto_increment,
description varchar(100) not null,
order_id
int
not null,
primary key (id),
constraint fk_order foreign key (order_id)
references orders(id)
);

class Order < ActiveRecord::Base
has_many :order_lines
end
class OrderLine < ActiveRecord::Base
belongs_to :order
end
one to many bet ween
orders and order lines
“has_many” is actually a
class level method call
that generates instance
methods

my_order = Order.find(id)
has_order_lines = my_order.order_lines?
order_lines_count = my_order.order_lines.size
my_order.order_lines.push(new_order, another_new_order)
specific_order_line = my_order.find(....)
specific_order_lnes = my_order.find_by_description(“abc”)
my_line = OrderLine.find(15)
has_owning_order = my_line.order.nil?
old_order = my_line.order
my_line.order= another_order

Validation

quick summary
Gross Income $ 0 Total Tax $ 0
Adjusted Gross Income $ 0 Total Payments $ 0
Total Deductions $ 16,400 Refund Amount $ * confirmation checks t wo
0
Total Taxable Income $ 0 Amount You Owe $ password0fields against each
to file your 2005 federal extension, simply follow these instructions
other
STEP A - Once your e-filed extension has been accepted, you will acceptance is pattern of
*
receive an email with a confirmation number. Enter the confirmation
number on your printed copy of Form 4868 and keep for your records. of ser vice/agreement
terms
checkbox
STEP B - Since you indicated that you are not paying an amount with
Form 4868, there is nothing to mail.
For more information about tax, mortgage and financial services call 1-800-HRBLOCK or visit hrblock.com

quick summary
Gross Income $ 0 Total Tax $ 0
Adjusted Gross Income $ 0 Total Payments $ 0
Total Deductions $ 16,400 Refund Amount $ 0
Total Taxable Income $ 0 Amount You Owe $ 0
to file your 2005 federal extension, simply follow these instructions
STEP A - Once your e-filed extension has been accepted, you will
receive an email with a confirmation number. Enter the confirmation
number on your printed copy of Form 4868 and keep for your records.
STEP B - Since you indicated that you are not paying an amount with
Form 4868, there is nothing to mail.
For more information about tax, mortgage and financial services call 1-800-HRBLOCK or visit hrblock.com

Much More...
• many to many via has_many :through
• eager loading
• acts_as_list, acts_as_tree
• single table inheritance
• callbacks and observers

ActionController

http://url.com/weblog/
aka
http://url.com/weblog/index.rhtml

/app/controllers/weblog_controller.rb:
class WeblogController < ActionController::Base
layout "weblog/layout"
def index
@posts = Post.find_all
end
def display
@post = Post.find(:params[:id])
||= conditional assignment
end operator
def new cart is a non persistent model
@post = Post.new object used for storing/calculating
products
end
“the flash” = place to throw stuff
def create like response messages, error
@post = Post.create(params[:post]) reports that accumulate as a
request is processed
redirect_to :action => "display", :id => @post.id
end
end

/app/views/weblog/layout.rhtml:
<html><body>
<%= @content_for_layout %>
</body></html>
/app/views/weblog/index.rhtml:
<% for post in @posts %>
<p><%= link_to(post.title, :action => "display", :id => post.id %></p>
<% end %>
/app/views/weblog/display.rhtml:
<p>
<b><%= post.title %></b><br/>
<b><%= post.content %></b>
</p>
/app/views/weblog/new.rhtml:
<%= form "post" %>

http://url.com/weblog/display/5
http://url.com/weblog/display/123
http://url.com/weblog/new/

ActionPack features
• rxml - XML Builders
• rhtml - HTML templates
• helpers - module to assist the view
• form and field helpers
• layouts and partials - similiar to tiles
• page caching and fragment caching

! &'())*+,%-.,//".0.1
!"#'4,+:
''!3&4$'('J&4$7!5,K"#$#%&B*+,CL
"%!
" "!$-0.2-&/
>D('?9$%E:#F'*#8:+95'(-'G&#A4G2'*+,'(-'!3&4$'D-
>D(':4H:E!4I,'''''''''''G3&4$G2'G5#%4G''D->@"-
>D(':4H:E!4I,'''''''''''G3&4$G2'G8935:$;G''D->@"-
>D('"#&&<9$,E!4I,'G3&4$G2'G"#&&<9$,G''D->@"-
7'7'7
! NO4'#""I+8#:+95'$484+A4&'#'$4P34&:'
>D('45,E?9$%E:#F'D-
:9'4,+:'#'3&4$7'Q:'$4#,&':O4',#:#'+5:9'
#'54<'J&4$'%9,4I'9MR48:7 hash created with user
attributes for easy
" NO4'4,+:7$O:%I':4%"I#:4'+&'8#II4,7'Q:' update/save
3&4&':O4'+5?9$%#:+95'+5':O4'3&4$'
9MR48:':9'F454$#:4777
# >?9$%'#8:+95(6@%;#""@&#A4@./016-
''''>+5"3:'5#%4(63&4$B5#%4C6'777'- field helpers make input
# :O4'SNTU'+&'&45:':9':O4'M$9<&4$7'
''''>+5"3:'5#%4(63&4$B8935:$;C6'777'-
(s) easy
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''''7'7'7
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"#$#%4:4$&':9'!5,':O4'3&4$'$489$,'
#5,'3",#:4'+:7 $ !"#$#%&'(')
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=
''$#'3&4$73",#:4E#::$+M3:4&K"#$#%&B*3&4$CL
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Figure 17.2: Models, Controllers, and Views Work Together

Ajax Support
• Ajax support built in since March ’05
• Built on Prototype and Scriptaculous
• Updating forms and tables via Ajax is trivial
• Best Ajax support of any web framework

Other Stuff
• Awesome Testing support built in
• Generators/scaffolding
• Migrations - refactor your database
• Capistrano - automate deployment
• Huge, helpful community

But Does it Scale?

Yes.

• scales just like Yahoo! , LiveJournal, etc
• share nothing
• load balance to each tier
• add servers as needed

http://www.rubyonrails.com/applications

Why Not Rails?

• Legacy databases
• Tool support
• Deployment is hard
• Internationalization
• Its different
• Its advanced

The Future
• Rails growth will continue
• Its influence is already felt everywhere
• JRuby could be huge
• Its biggest impact may be felt in future
frameworks

No mater what, its going to be a
fun ride.

Thank You!