Depurando una Ejecución con Ruby

[~/sinatra/sinatra-debug/example1]$ ls 
Gemfile           Rakefile          my_sinatra.rb
Gemfile.lock      config.ru         rackmiddleware.rb

[~/sinatra/sinatra-debug/example1]$ cat Gemfile
source 'http://rubygems.org'

group :development, :test do
  gem 'awesome_print'
  gem 'racksh'
  gem 'debugger'
  gem 'pry'
  gem 'pry-debugger'
end

[~/sinatra/sinatra-debug/example1]$ cat my_sinatra.rb 
# my_sinatra.rb
require 'debugger'
require 'sinatra'
require './rackmiddleware'
use RackMiddleware
get '/:p' do |x|
   # debugger
  "Welcome to #{x}"
end

[~/sinatra/sinatra-debug/example1]$ cat rackmiddleware.rb 
class RackMiddleware
  def initialize(appl)
    @appl = appl
  end

  def call(env)
    debugger
    start = Time.now
    status, headers, body = @appl.call(env) # call our Sinatra app
    stop = Time.now
    puts "Response Time: #{stop-start}" # display on console
    [status, headers, body]
  end
end

[~/sinatra/sinatra-debug/example1]$ ruby my_sinatra.rb 
== Sinatra/1.4.3 has taken the stage on 4567 for development with backup from Thin
>> Thin web server (v1.5.1 codename Straight Razor)
>> Maximum connections set to 1024
>> Listening on localhost:4567, CTRL+C to stop

Al conectar al servidor queda en espera:

[~/sinatra/sinatra-debug]$ curl 'http://localhost:4567/canarias'

En la otra terminal el servidor se detiene en el primer breakpoint señalado:

[~/sinatra/sinatra-debug/example1]$ ruby my_sinatra.rb 
== Sinatra/1.4.3 has taken the stage on 4567 for development with backup from Thin
>> Thin web server (v1.5.1 codename Straight Razor)
>> Maximum connections set to 1024
>> Listening on localhost:4567, CTRL+C to stop
/Users/casiano/Dropbox/src/ruby/sinatra/sinatra-debug/example1/rackmiddleware.rb:8
start = Time.now

[3, 12] in /Users/casiano/Dropbox/src/ruby/sinatra/sinatra-debug/example1/rackmiddleware.rb
   3      @appl = appl
   4    end
   5  
   6    def call(env)
   7      debugger
=> 8      start = Time.now
   9      status, headers, body = @appl.call(env) # call our Sinatra app
   10      stop = Time.now
   11      puts "Response Time: #{stop-start}" # display on console
   12      [status, headers, body]

Ahora podemos ir paso a paso e inspeccionar variables:

(rdb:1) p start
2013-07-04 15:40:11 +0100
(rdb:1) n
/Users/casiano/Dropbox/src/ruby/sinatra/sinatra-debug/example1/rackmiddleware.rb:10
stop = Time.now

[5, 14] in /Users/casiano/Dropbox/src/ruby/sinatra/sinatra-debug/example1/rackmiddleware.rb
   5  
   6    def call(env)
   7      debugger
   8      start = Time.now
   9      status, headers, body = @appl.call(env) # call our Sinatra app
=> 10      stop = Time.now
   11      puts "Response Time: #{stop-start}" # display on console
   12      [status, headers, body]
   13    end
   14  end
(rdb:1) p body
["Welcome to canarias"]
(rdb:1) p status
200
(rdb:1) p headers
{"Content-Type"=>"text/html;charset=utf-8", "Content-Length"=>"19"}