How to Use Pry with Sinatra

How to use Pry with Sinatra?

Summary

Use require 'pry' at the top of your application.
Call binding.pry in your code whenever you want to drop into the interactive session. For information on using Pry, see Turning IRB on its head with Pry and the Pry wiki.
When you are done with a particular interactive session, type exit or Ctrl-D; Sinatra will resume running where it left off.

Example

require 'sinatra'
require 'pry'

get '/' do
  @cats = rand(100)
  html = haml :index
  binding.pry
  html
end

__END__
@@index
%html
  <head><title>Hello World</title></head>
  %body
    %p I have #{@cats} cat#{:s unless @cats==1}!

Here's what it looks like when I start the web server:

C:\>ruby pry_into_sinatra.rb
== Sinatra/1.2.6 has taken the stage on 4567 for development with backup from Thin
>> Thin web server (v1.2.11 codename Bat-Shit Crazy)
>> Maximum connections set to 1024
>> Listening on 0.0.0.0:4567, CTRL+C to stop

When I make a request in a web browser to http://localhost:4567 the console drops into the Pry debugger before sending the result:

From: pry_into_sinatra.rb @ line 7 in Sinatra::Application#HEAD /:

     2: require 'pry'
     3:
     4: get '/' do
     5:         @cats = rand(100)
     6:         html = haml :index
 =>  7:         binding.pry
     8:         html
     9: end
    10:
    11: __END__
    12: @@index
pry(#<Sinatra::Application:0x3300ac8>)> @cats
=> 42
pry(#<Sinatra::Application:0x3300ac8>)> puts html
<html>
  <head><title>Hello World</title></head>
  <body>
    <p>I have 42 cats!</p>
  </body>
</html>
=> nil
pry(#<Sinatra::Application:0x3300ac8>)> exit
127.0.0.1 - - [24/Aug/2011 13:25:57] "GET / HTTP/1.1" 200 96 28.5390
127.0.0.1 - - [24/Aug/2011 13:25:57] "GET /favicon.ico HTTP/1.1" 404 447 0.0010

Further Debugging

If you want to be able to use traditional debugging commands, such as setting line-based breakpoints, or stepping, or breaking when exceptions are raised, see the PryDebug library by Mon-Ouie.

Using pry with Sinatra

It all depends on where you want to use pry. If you want it to work everywhere in your Sinatra project, then just add it to your Gemfile.

group :development, :test do
   gem 'pry'
end

I would recommend limiting the environments to :development and :test, since you will be doing your debugging there.

You can also require it in the top of your application like so:

require 'pry'

Debugging Sinatra application

In your Gemfile:

gem "pry"
gem "pry-nav"

Run bundle. Then whenever the script encounters binding.pry, you will have a shell opened. You can see where you are with whereami, you move to the next line with next, continue running the script with continue. If you want to inspect a variable, just type its name.

See pry-nav for more info.

How to use pry to access a Rack middleware instance?

Not sure what you are trying to do, but you can

Monkey patch the middleware class to use pry inside
connect directly from the source code (what I understood you dont want)
play around with the "use" method from Sinatra to access the middleware you want from the middleware stack

That are my ideas, hope it helps

AFTER YOUR EDITED:

Check out this, you can access the @middleware instance variable to get the used middlewares

How do you debug a Sinatra app like a Rails app?

You could try adding a before filter that prints out the parameters

before do
  puts '[Params]'
  p params
end

How to Use Pry with Sinatra