Building Web Apps with Rack and Sinatra

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Building Web Apps with Rack and Sinatra @blacktm

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Objectives ✔ Describe the HTTP request process ✔ Define Rack, describe its purpose ✔ Build a simple Rack web app ✔ Define, build, and use middleware ✔ Define DSL (compare with “framework”) ✔ Build a simple Sinatra app

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Things You’ll Need ✔ gem install thin ✔ gem install sinatra ✔ gem install heroku ✔ Project ﬁles and notes at blacktm.com

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HTML CSS JS Rails / Sinatra Ruby Deploy

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Web Server HTTP Request Middleware Rack Your App

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Web Server HTTP Request Middleware Rack Your App

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What is Rack? A modular web server interface. (Connects your Ruby app to the web.)

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A common interface.

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Your App Rack Thin WEBrick Mongrel CGI

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What is a Rack app? A Ruby object that responds to a “call” method, taking a single hash parameter, and returning an array which contains the response status code, response headers, and response body as an array of strings. “In English, please.”

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$ rackup config.ru Run it! Open “simple_rack” and edit the “conﬁg.ru” ﬁle. # config.ru - rackup file require 'rack' class MyApp def call(env) headers = { "Content-Type" => "text/html" } [200, headers, ["Hello world!"]] end end run MyApp.new

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http://0.0.0.0:9292 #=> Hello world! http://0.0.0.0:9292/there/isnt/a/route/here #=> Hello world! A very basic server.

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Who cares? ✔ You just built a web app. Damn. ✔ Important in understanding (and building) web frameworks (e.g. Rails) ✔ Middleware!

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HTTP Request Middleware Rack Your App Web Server

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HTTP Request Middleware Rack Your App Web Server

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Let’s explore Middleware! 1. Open “rack_middleware” 2. Stop the server (ctrl-c) 3. Run: $ rackup config.ru 4. Open: http://0.0.0.0:9292 or: http://localhost:9292

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Rack’s Default Middleware (in development mode): Rack::CommonLogger Rack::ShowExceptions Rack::Lint

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# app.rb class MyApp def call(env) puts "Hello from MyAPP" return [200, {}, ["Hello"]] end end No “Content-Type”

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Solution? Middleware!

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class ContentType def initialize(app) @app = app end def call(env) status, headers, body = @app.call(env) puts "Hello from ContentType" # TODO: Add "Content-Type" to the HTTP # headers and return the response. end end Open “conﬁg.ru”

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Add the “Content-Type” to the headers. # TODO: Add "Content-Type" to the HTTP # headers and return the response. headers.merge!( "Content-Type" => "text/html" ) return [status, headers, body]

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class FinishSentence def initialize(app) @app = app end def call(env) status, headers, body = @app.call(env) puts "Hello from FinishSentence" # TODO: Add " world!" to the HTTP # body and return the response. end end

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Add the “ world!” to the body. # TODO: Add " world!" to the HTTP # body and return the response. body.push(" world!") return [status, headers, body]

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Use the middleware. # TODO: Tell the app to use the "ContentType" # and "FinishSentence" middleware. use ContentType use FinishSentence

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Run it! $ rackup config.ru http://0.0.0.0:9292 127.0.0.1 - - [13/Oct/2012 21:18:58] "GET / HTTP/1.1" 200 12 0.0009

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rack_middleware:$ rackup config.ru >> Thin web server (v1.5.0 codename Knife) >> Maximum connections set to 1024 >> Listening on 0.0.0.0:9292, CTRL+C to stop Hello from MyAPP Hello from FinishSentence Hello from ContentType 127.0.0.1 - - [14/Nov/2012 17:01:07] "GET / HT {

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What’s wrong with this?

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What’s wrong with this?

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“Sinatra is a DSL for quickly creating web applications in Ruby with minimal e ort.” A “human interface” to Rack. “Domain Specific Language”

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HTTP Request Middleware Rack Your App Web Server

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HTTP Request Middleware Rack Your App Web Server

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HTTP Request Middleware Rack Your App Sinatra Web Server

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The Showdown Plain ‘ol Rack Sinatra get '/' do "Hello world!" end class MyApp def call(env) headers = { "Content-Type" => "text/html" } [200, headers, ["Hello world!"]] end end

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$ rackup config.ru Run it! Open “simple_sinatra” and edit the “conﬁg.ru” ﬁle. # config.ru require 'sinatra' get '/' do "Hello Sinatra!" end run Sinatra::Application

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What else can do?

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# config.ru require 'sinatra' get '/' do "Hello Sinatra!" end get '/hello/:name' do |n| "Hello #{n}!" end get '/wildcard/*' do request.inspect end error 404 do "OMG, 404!" end get '/breakit' do 500 end run Sinatra::Application

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Rails email database ajax orm csrf routes tests sessions models views controllers “A full-stack web application framework.” logging tasks

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Middleware Rack Your App Rails Web Server Middleware Rack Your App Sinatra Web Server

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Middleware Rack Your App Web Server Middleware Rack Your App Sinatra Web Server RAILS