This document provides an overview and introduction to using the Sinatra web framework for building RESTful web applications in Ruby. It discusses Sinatra's philosophy of being simple and easy to use, introduces REST principles and how Sinatra supports them through HTTP verbs, routing, caching, authentication and more. Code examples are provided to demonstrate how a basic "Hello World" application is structured in Sinatra and how requests are routed and executed under the hood.

1. REST with Sinatra
Emanuele DelBono
@emadb

2. Thanks to the sponsors

3. About me
I’m a software developer in
CodicePlastico.
I write Web applications in C# with
ASP.NET MVC. I’m a member of
<WEBdeBS/> a local web
community.
...and I’m a wannabe Ruby
developer ;-)

4. Agenda
‣ Philosophy.
Sweet and easy.
‣ REST.
Yet another boring introduction.
‣ Hello world.
Show some magic.
‣ Features.
Amazing!
‣ Inside.
How it works?
‣ Q&A.
...and thanks.

5. Sinatra as a REST server

6. What is isn’t
‣ Sinatra is not
-another MV* framework
-a full framework like Rails
-an ORM
-a game project

7. Sinatra is just a DSL
written in ruby

8. Hello world

9. Hello world
~$ gem install sinatra
~$ vi app.rb

10. Hello world
~$ gem install sinatra
~$ vi app.rb
require 'sinatra'
get '/' do
'hello world!'
end

11. Hello world
~$ gem install sinatra
~$ vi app.rb
require 'sinatra'
get '/' do
'hello world!'
end
~$ ruby app.rb

13. Is it really so easy?
‣ Yep! (special thanks to Ruby
sweeties)
- get is a just a method (more later)
- the route is the parameter
- the block is what should be
executed
- the block returns the result
- the server is built in (based on Rack)

14. Let’s go REST
What? Yet another REST introduction?

16. 5 REST principles
‣ Uniform Interface
‣ HATEAOS
‣ Stateless
‣ Cacheable
‣ Client-Server
‣ Layered System

17. Sinatra and REST
‣ Sinatra supports
- All HTTP verbs
- Caching
- Content types
- Routes
- ....and all you need to build a rest server

18. Give a look at the

19. Verbs
‣ Support for all verbs
- Get, Post, Put, Delete, Head, Options,
Patch
‣ They are just methods

20. Routing
‣ No need of route files or route
maps
‣ The verb method takes the route
as parameter

21. Routing
get ( ‘/todos’ ) {...}
get ( ‘/todo/:id’ ) {...}
get ( ‘/*’ ) {...}

22. Routing Conditions
get '/foo', :agent => /Mozilla/(d.d)s
w?/ do
"You're using Mozilla version
#{params[:agent][0]}"
end
get '/foo' do
# Matches non-Mozilla browsers
end

23. Routing Custom
set(:prob) { |v| condition { rand <= v } }
get '/win_a_car', :prob => 0.1 do
"You won!"
end
get '/win_a_car' {"Sorry, you lost."}

24. Xml or Json
‣ You can set the content_type to
whatever you need
content_type :json
content_type :xml

25. Status codes
‣ Set the HTTP status code is
status 200
status 403

26. Http Headers
‣ You can add your own headers
headers "X-My-Value" => "this is my
header"

27. Redirect
redirect to ‘/todos’

28. Cache
‣ You can set your cache information
using the headers method
headers "Cache-Control" => "public,
must-revalidate, max-age=3600",
"Expires" => Time.at(Time.now.to_i + (60

29. Cache
‣ Or better, you can use the expires
expires 3600, :public

30. Filters
before do
#...
end
after do
#...

31. Authentication
‣ Basic authentication support through
Rack
‣ Key-based authentication

32. Basic Authentication
use Rack::Auth::Basic, "Private area" do
|usr, pwd|
[usr, pwd] == ['admin', 'admin']
end

33. Token authentication
before do
if env[‘HTTP_MY_KEY’] ==’rubyrocks‘
error 401
end
end

34. Demo

35. Stream
‣ Supports streamed content
‣ Streamed responses have no Content-
Length header
‣ But have Transfer-Encoding: chunked

36. Inside

37. Inside
‣ Sinatra source code is on github:
http://github.com/sinatra/sinatra
‣ Less than 2k lines of code
‣ Based on Rack

38. Application style
Classic application
vs
Modular application

39. Classic App
Single file
Standalone

40. Modular Apps
Multi file
Subclassing Sinatra::Base
Distributed as library

41. The code
What happen when a request arrives?
get (‘/hello’) do { ‘hello world’ }

42. Where do get come from?
require "sinatra"
outer_self = self
get '/' do
"outer self: #{outer_self}, inner self: #{self}"
end
outer self: main, inner self: #<Sinatra::Application:
closures in ruby are “scope gate”

44. $ irb

45. $ irb
ruby-1.9.2-p180 > require 'sinatra'

46. $ irb
ruby-1.9.2-p180 > require 'sinatra'
=> true

47. $ irb
ruby-1.9.2-p180 > require 'sinatra'
=> true
ruby-1.9.2-p180 > method(:get)

48. $ irb
ruby-1.9.2-p180 > require 'sinatra'
=> true
ruby-1.9.2-p180 > method(:get)
=> #<Method: Object(Sinatra::Delegator)#get>

49. $ irb
ruby-1.9.2-p180 > require 'sinatra'
=> true
ruby-1.9.2-p180 > method(:get)
=> #<Method: Object(Sinatra::Delegator)#get>
ruby-1.9.2-p180 > Sinatra::Delegator.methods(false)

50. $ irb
ruby-1.9.2-p180 > require 'sinatra'
=> true
ruby-1.9.2-p180 > method(:get)
=> #<Method: Object(Sinatra::Delegator)#get>
ruby-1.9.2-p180 > Sinatra::Delegator.methods(false)
=> [:delegate, :target, :target=]

51. $ irb
ruby-1.9.2-p180 > require 'sinatra'
=> true
ruby-1.9.2-p180 > method(:get)
=> #<Method: Object(Sinatra::Delegator)#get>
ruby-1.9.2-p180 > Sinatra::Delegator.methods(false)
=> [:delegate, :target, :target=]
ruby-1.9.2-p180 > Sinatra::Delegator.target

52. $ irb
ruby-1.9.2-p180 > require 'sinatra'
=> true
ruby-1.9.2-p180 > method(:get)
=> #<Method: Object(Sinatra::Delegator)#get>
ruby-1.9.2-p180 > Sinatra::Delegator.methods(false)
=> [:delegate, :target, :target=]
ruby-1.9.2-p180 > Sinatra::Delegator.target
=> Sinatra::Application

53. $ irb
ruby-1.9.2-p180 > require 'sinatra'
=> true
ruby-1.9.2-p180 > method(:get)
=> #<Method: Object(Sinatra::Delegator)#get>
ruby-1.9.2-p180 > Sinatra::Delegator.methods(false)
=> [:delegate, :target, :target=]
ruby-1.9.2-p180 > Sinatra::Delegator.target
=> Sinatra::Application
ruby-1.9.2-p180 > Sinatra::Application.method(:get)

54. $ irb
ruby-1.9.2-p180 > require 'sinatra'
=> true
ruby-1.9.2-p180 > method(:get)
=> #<Method: Object(Sinatra::Delegator)#get>
ruby-1.9.2-p180 > Sinatra::Delegator.methods(false)
=> [:delegate, :target, :target=]
ruby-1.9.2-p180 > Sinatra::Delegator.target
=> Sinatra::Application
ruby-1.9.2-p180 > Sinatra::Application.method(:get)
=> #<Method:
Sinatra::Application(Sinatra::Base).get>

55. Where do get come from?
‣ get is defined twice:
– Once in Sinatra::Delegator a mixin
extending Object
– Once in Sinatra::Application
‣ The Delegator implementation simply
delegate to Application
‣ That’s why we have get/post/...
methods on main

56. How the block is invoked?
‣ The route! method finds the correct
route
def route_eval
throw :halt, yield
end
‣ throw is used to go back to the invoker

57. In base.rb
‣ The invoker
def invoke
res = catch(:halt) { yield }
# .... other code...
end

58. It’s a kind of magic!

59. Sinatra has ended his set
(crowd applauds)

60. Questions?

61. demos at:
http://github.com/emadb/
webnetconf_demo

62. Please rate this session
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