How to use Pry with Sinatra?
Summary
- Use
require 'pry'at the top of your application. - Call
binding.pryin 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
exitor 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 htmlend__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 stopWhen 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: @@indexpry(#<Sinatra::Application:0x3300ac8>)> @cats=> 42pry(#<Sinatra::Application:0x3300ac8>)> puts html<html> <head><title>Hello World</title></head> <body> <p>I have 42 cats!</p> </body></html>=> nilpry(#<Sinatra::Application:0x3300ac8>)> exit127.0.0.1 - - [24/Aug/2011 13:25:57] "GET / HTTP/1.1" 200 96 28.5390127.0.0.1 - - [24/Aug/2011 13:25:57] "GET /favicon.ico HTTP/1.1" 404 447 0.0010Further 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.
Load the application into a Pry session:
Take a look at your config.ru. If it looks something like this:
require File.join(File.dirname(__FILE__), 'config', 'application.rb')you can load your application into Pry using
bundle exec pry -I . -r config/application.rb# where -I . adds current dir to load path# and -r is the file you want to requireThis can be done with any module or class so long as dependencies are met.
Look at this Pry cheat sheet for advanced examples of Pry usage.
I prefer pry-debugger. However there is still trick, that you can not pry-stepping while you run sinatra under classic style.
In order to find the best way to debug sinatra app, I created a repo at github, which looks like below.
Here is the repo: https://github.com/hlee/sinatra_debugger_example