Menu
I am writing my first Sinatra application and would like to use Pry to inspect/debug some things going on in the application. I haven't used Pry before either, but I would like to try it out. How would I get started using Pry with my Sinatra application?
725
Pry is like IRB on steroids Both IRB and Pry use REPL commands: Read, Evaluate, Print, and Loop. But Pry allows you to go further when debugging. For example, Pry gives you color-coded syntax, which helps when you're trying to figure out what will happen when code is executed.
require 'pry' at the top of your application.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.exit or Ctrl-D; Sinatra will resume running where it left off.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
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.
179
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 require
This 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.
6
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
4
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
