Introduction to rack

1. INTRO TO RACK
@revathskumar

2. ABOUT
Rubyist / JavaScripter
Team Member / /
Works at
Blog at
Twitter/Github -
Google+:
Yeoman @keralarb @keralajs
@whatznear
blog.revathskumar.com
@revathskumar
+RevathSKumar

3. A MODULAR RUBY WEBSERVER INTERFACE

4. BASIC RACK APP
require 'rack'
app = Proc.new do | env |
[200, {'Content-Type' => 'text/html'}, ['My first Rack app']]
end
Rack::Handler::WEBrick.run app

5. MIDDLEWARES
a way to filter a request and response

6. ANY RUBY OBJECT WHICH RESPONDS TO
CALL
AND RETURN ARRAY OF 3 ELEMENTS

7. CALL ACCEPTS ENV

8. BASIC MIDDLEWARE
class BasicMiddleware
def initialize next_in_chain
@app = next_in_chain
end
def call env
@app.call(env)
end
end

9. MIDDLEWARE CAN CALL EACH OTHERS TO
CHAIN ACTIONS

10. SO ORDER MATTERS

11. MIDDLEWARE CHAIN
class Mware
def initialize next_in_chain
@app = next_in_chain
end
def call env
@app.call(env)
end
end
class Mware1
def call env
[200, {'content-type' => 'text/html'}, ["Hello Mware1"]]
end
end
app = Proc.new do | env |
Mware.new(Mware1.new).call(env)
end

12. RACK::BUILDER
IMPLEMENTS A SMALL DSL TO ITERATIVELY CONSTRUCT
RACK APPLICATIONS.

13. require 'rack'
app = Rack::Builder.new do
use Rack::CommonLogger
run Proc.new do | env |
[200, {'Content-Type' => 'text/html'}, ['Using builder']]
end
end
Rack::Handler::WEBrick.run app

14. app = Proc.new { | env |
stack = [ proc {|app| Mware.new app }, proc {|app| Mware1.new app } ]
mware_obj = stack.reverse.inject(self){ | prev, curr|
curr[prev] # curr.call(prev)
}
mware_obj.call(env)
}

15. ROUTES
require 'rack'
app = Rack::Builder.new do
use Rack::CommonLogger
map '/index' do
run Proc.new do | env |
[200, {'Content-Type' => 'text/html'}, ['Index']]
end
end
run Proc.new do | env |
[200, {'Content-Type' => 'text/html'}, ['Root']]
end
end
Rack::Handler::WEBrick.run app

16. NESTED ROUTES
require 'rack'
app = Rack::Builder.new do
# ...
map '/index' do
# ...
map '/1' do
run Proc.new do | env |
[200, {'Content-Type' => 'text/html'}, ['Index 1 ']]
end
end
end
# ...
end
Rack::Handler::WEBrick.run app

17. VIEW
class Basic
def initialize app
@index = File.read("index.html")
end
def call env
[200, {'Content-Type' => 'text/html'}, [@index]]
end
end
require 'rack'
app = Rack::Builder.new do
use Rack::CommonLogger
run Basic.new
end
Rack::Handler::WEBrick.run app

18. RENDERING ERB
require "erb"
class Basicerb
attr_reader :rendered_html
def initialize name
@name = name
@template = File.read('./index.erb')
end
def render
ERB.new(@template, 0, "", "@rendered_html").result binding
self
end
def call app
[200, {'Content-Type' => 'text/html'}, [render.rendered_html]]
end
end

19. ERB: LAYOUT & VIEW
def initialize name
@name = name
@layout = File.read('./layout.erb')
@template = File.read('./index.erb')
end
def render
templates = [@template, @layout]
@rendered_html = templates.inject(nil) do | prev, temp |
_render(temp) { prev }
end
self
end
def _render temp
ERB.new(temp).result( binding )
end

20. RACK::STATIC
Serve static files
require 'rack'
builder = Rack::Builder.new do
use Rack::CommonLogger
use Rack::Static, :urls => ['/bower_components/', '/assets/'], root: '.'
end
Rack::Handler::WEBrick.run builder

21. RACK CONTRIB
A collection of middlewares.
rack/rack-contrib

22. USING RACKUP
# config.ru
run Proc.new do | env |
[200, {'Content-Type' => 'text/html'}, ['My first Rack app']]
end
~$ rackup

23. READ CONFIG.RU OR SUPPLIED CONFIG FILE
CONVERT TO A INSTANCE OF RACK::BUILDER
config_file = File.read(config)
rack_application = eval("Rack::Builder.new { #{config_file} }")

24. QUESTIONS?
Revath S Kumar
Github/Twitter: @revathskumar
blog.revathskumar.com