#317 Rack App from Scratch pro

Jan 16, 2012 | 15 minutes | Tools, Rack

Rack comes with many helpful utilities such as request and response objects, various middleware, and MockRequest for testing. Here I cover all of these while building a Rack app from scratch.

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          terminal
        
gem install rack
rackup -Ilib
ruby greeter_test.rb

          config.ru
        
require "greeter"

use Rack::Reloader, 0
use Rack::Auth::Basic do |username, password|
  password == "secret"
end

run Rack::Cascade.new([Rack::File.new("public"), Greeter])

          lib/greeter.rb
        
require "erb"

class Greeter
  def self.call(env)
    new(env).response.finish
  end
  
  def initialize(env)
    @request = Rack::Request.new(env)
  end
  
  def response
    case @request.path
    when "/" then Rack::Response.new(render("index.html.erb"))
    when "/change"
      Rack::Response.new do |response|
        response.set_cookie("greet", @request.params["name"])
        response.redirect("/")
      end
    else Rack::Response.new("Not Found", 404)
    end
  end
  
  def render(template)
    path = File.expand_path("../views/#{template}", __FILE__)
    ERB.new(File.read(path)).result(binding)
  end
  
  def greet_name
    @request.cookies["greet"] || "World"
  end
end

          lib/views/index.html.erb
        
<!DOCTYPE html>
<html>
  <head>
    <title>Greeter</title>
    <link rel="stylesheet" href="/stylesheets/application.css" type="text/css" charset="utf-8">
  </head>
  <body>
    <div id="container">
      <h1>Hello <%= greet_name %>!</h1>
      <form method="post" action="/change">
        <input name="name" type="text">
        <input type="submit" value="Change Name">
      </form>
    </div>
  </body>
</html>

          greeter_test.rb
        
require "rubygems"
require "rack"
require "minitest/autorun"
require File.expand_path("../lib/greeter", __FILE__)

describe Greeter do
  before do
    @request = Rack::MockRequest.new(Greeter)
  end

  it "returns a 404 response for unknown requests" do
    @request.get("/unknown").status.must_equal 404
  end

  it "/ displays Hello World by default" do
    @request.get("/").body.must_include "Hello World!"
  end

  it "/ displays the name passed into the cookie" do
    @request.get("/", "HTTP_COOKIE" => "greet=Ruby").body.must_include "Hello Ruby!"
  end

  it "/change sets cookie and redirects to root" do
    response = @request.post("/change", params: {"name" => "Ruby"})
    response.status.must_equal 302
    response["Location"].must_equal "/"
    response["Set-Cookie"].must_include "greet=Ruby"
  end
end