REST with Sinatra
Emanuele DelBono
@emadb

Thanks to the sponsors

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 ;-)

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.

Sinatra as a REST server

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

Sinatra is just a DSL
written in ruby

Hello world

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

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

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

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)

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

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

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

Give a look at the

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

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

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

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

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."}

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

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

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

Redirect
redirect to ‘/todos’

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

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

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

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

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

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

Demo

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

Inside

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

Application style
Classic application
vs
Modular application

Classic App
Single file
Standalone

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

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

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”

$ irb

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

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

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

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

$ 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)

$ 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=]

$ 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

$ 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

$ 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)

$ 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>

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

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

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

It’s a kind of magic!

Sinatra has ended his set
(crowd applauds)

Questions?

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

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