The document discusses the Rack web server interface used in Ruby and provides examples of using Rack to build simple web applications that respond with "Hello World". It also shows how middleware can be used in Rack applications to add functionality like response timing.

1. WHAT THE RACK ?!

2. O QUE É ?

3. app.call(env)

4. , …
REQUEST_METHOD: HEAD
REQUEST_PATH: /
PATH_INFO: /
REQUEST_URI: /
HTTP_VERSION: HTTP/1.1
HTTP_USER_AGENT: curl/7.21.4 (universal-apple-
darwin11.0) libcurl/7.21.4 OpenSSL/0.9.8r zlib/1.2.5
HTTP_HOST: localhost:3000
HTTP_ACCEPT: ! '*/*'
GATEWAY_INTERFACE: CGI/1.2
SERVER_PORT: '3000’
… -

5. app.call(env)
=> *200, ,‘Content-Type’=> ‘text/plain’ -, ‘Hello World !’+

6. Require ‘thin’
Rack::Handler::Thin.run(app, port: 4000)

7. WRITE ONCE, SERVE
EVERYWHERE !

8. class HelloWorld
def initialize(name)
@name = name
end
def call(env)
*200, , ‘Content-Type’ => ‘text/plain’ -
end
end
require ‘rubygems
require ‘rack’
Rack::Handler::Mongrel.run(HelloWorld.new(“Dan”), port: 4000)

9. MIDDLEWARE

10. class ResponseTimer
def initialize(app, message = "Response Time")
@app = app
@message = message
end
def call(env)
start = Time.now
status, headers, response = @app.call(env)
stop = Time.now
if headers["Content-Type"].include? "text/html"
[status, headers, "<!-- #{@message}: #{stop - start} -->n" +
response.body]
else
[status, headers, response]
end
end
end

11. Rails::Initializer.run do |config|
config.middleware.use "ResponseTimer", "Load Time"
end