#280 Pry with Rails

Aug 22, 2011 | 8 minutes | Tools, Plugins

Pry is an alternative to IRB and sports many great features. Here I show how to integrate it into a Rails app, and how it can aid in debugging.

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J over 13 years ago

Anyone else experiencing problems with reloads for 'edit-method' and command line vim ?

It doesn't seem to reload the code after editing (:wq), only after another edit-method (so it looks like vim is handing back control to pry immediately after loading the file, and pry loads the unchanged module, rather than the changed one after save/quit).

Works with nano, though.

John Mair over 13 years ago

After editing the file in vim and exiting type load _file_ or reload-method Your#method_name to manually reload the file. (where _file_ is a special local representing the last file accessed by Pry)

Nate Bird over 13 years ago

Another great discovery Ryan! Do you know if Pry works with Ruby 1.8.7 or is it just for Ruby 1.9?

John Mair over 13 years ago

It should mostly work fine in 1.8.7 MRI and 1.8.7 RBX; i even backported Proc#source_location and Method#source_location so show-method and show-doc should work too, the only thing that doesnt work in 1.8.7 is source retrieval of methods defined inside the REPL; but it should be relatively rare you'd do this (i hope) :)

Frédéric over 13 years ago

Joshua Cheek's screeencast is also worth seeing, and includes a neater way to use Pry as IRB replacement for the rails console:

Simply add the following lines at the end of your config/environments/development.rb file, after the YourAppName::Application.configure block:

          ruby
        
silence_warnings do
  require 'pry'
  IRB = Pry
end

And no more need to use the longer pry -r config/environment to start the console: simply use the usual rails console/rails c command.

Tomek over 13 years ago

Great Tip! THX!
It is also worth noting that for this to work gem 'pry' must be in your Gemfile.

Tilo over 13 years ago

thank you Ryan!

finally a tool to see the source code of a method definition!
That was really a feature I missed from Lisp..

Bharat Ruparel over 13 years ago

Is anyone using Pry with Rails 3.1 RC5/RC6?
Thanks.
Bharat

Ken Hart over 13 years ago

I just set it up using RC6, it seems to be working just fine, is that not the case for you?

Bharat Ruparel over 13 years ago

Hello Ken,
Haven't tried yet. Thanks for letting me know. I will install it now.

Daniel Bruns over 13 years ago

I have to admit I was disappointed when I saw the topic for this week's railscast. The name and description just weren't what I was hoping for. Each week I look forward to learning a new way to use ruby/rails to solve problems by writing code. Pry was just a replacement for irb "UGH".

THEN . . . I watched it.

Wow. Thank you, Ryan. I'm betting that in less than a week, Pry will have saved me hours worth of time.

Lesson learned: Never judge Ryan's screencasts before watching them.

Daniel Palacio over 13 years ago

WOW !!!!! been using this the whole day.....this is freaking awesome. Just tested it with RC6 rails and Sinatra...I think this is the best day of this month !

dragosm over 13 years ago

Any way to replace the console with pry in 2.3.8 when you run

          ruby
        
ruby script/console

???

Wayne over 13 years ago

Yes, here is how to replace the rails console with pry

For those that don't like to click links:

          ruby
        
#config/environments/development.rb

MyApp::Application.configure do
  silence_warnings do
    begin
      require 'pry'
      IRB = Pry
      rescue LoadError
    end
  end
end

dragosm over 13 years ago

If i try
IRB = Pry
I get this:
ruby-1.8.7-p334/lib/ruby/1.8/irb/workspace.rb:19:in initialize': undefined methodconf' for Pry:Class (NoMethodError)
from /Users/dragos/.rvm/rubies/ruby-1.8.7-p334/lib/ruby/1.8/irb/context.rb:27:in new' from /Users/dragos/.rvm/rubies/ruby-1.8.7-p334/lib/ruby/1.8/irb/context.rb:27:ininitialize'
from /Users/dragos/.rvm/rubies/ruby-1.8.7-p334/lib/ruby/1.8/irb.rb:100:in new' from /Users/dragos/.rvm/rubies/ruby-1.8.7-p334/lib/ruby/1.8/irb.rb:100:ininitialize'
from /Users/dragos/.rvm/rubies/ruby-1.8.7-p334/lib/ruby/1.8/irb.rb:59:in new' from /Users/dragos/.rvm/rubies/ruby-1.8.7-p334/lib/ruby/1.8/irb.rb:59:instart'
from /Users/dragos/.rvm/rubies/ruby-1.8.7-p334/bin/irb:17

mayyang about 10 years ago

could u solved this problem? when i run '$irb' ,give me a message 'Unable to load pry', when i run '$require 'pry'' i got
"LoadError: no such file to load -- pry
from (irb):1:in `require'
from (irb):1
"

how could i fix it how could i use pry instead rib

mayyang about 10 years ago

how could i fix it how could i use pry instead rib

mayyang about 10 years ago

could u solved this problem? i didn't resolve, could u tell me, how can i do?

Chris Reid over 13 years ago

bye rails console

Nik over 13 years ago

Couldn't be more getting Pry right away: am running win764 bit, for some reason, I never can get color highlighting to work ANYWHERE; not even with a freshly installed system following every guide to the dot. If anyone here knows, please please enlighten.

fbehrens over 13 years ago

I once got some colorful working with ansicon and those .irbrc . Some more fiddling may be required, hope that helps, Frank

          ruby
        
require 'rubygems'
require 'win32console'
require 'term/ansicolor' 
include Win32::Console::ANSI
include Term::ANSIColor
require 'wirble'
Wirble.init
Wirble.colorize

NeilS over 13 years ago

Thanks for the the great RailsCast, Ryan - as always.

Has anyone figured out if it's possible to use 'binding.pry' for debugging if you're using Apache/Passenger rather than the built-in server?

StuFF mc about 13 years ago

I just realized it's why it's not stopping. I had moved to passenger. Did you find the solution?

John Mair about 13 years ago

Can you report this as an issue on https://github.com/pry/pry/issues with an exact explanation of your problem ?

dragosm over 13 years ago

Is there a way to reload the environment like
reload! from IRB ?

Thomas Watson Steen over 13 years ago

You can just type reload! in Pry as you are used to

Alexander over 13 years ago

Is there any way to let methods like "show-method, edit, etc." use vim without binding to default editor?

John Mair over 13 years ago

you can set the environment variable $EDITOR in your shell instead and Pry will use that. Why do you want to avoid setting Pry.config.editor btw?

Alexander over 13 years ago

I like vim but my colleagues not loving it and i can't use it as default on common server. But when i run pry $EDITOR=vim it still use nano =(

fbehrens over 13 years ago

For Windows users, the amazing reloading mechanism on edit-method works fine when using GVIM and set EDITOR=vim

harryhorn over 13 years ago

Thanks for the great screencast.

For those who wish to use Hirb with Pry add the following to your ~/.pryrb file

          ruby
        
require 'hirb'

Hirb.enable

Pry.config.print = proc do |output, value|
  Hirb::View.view_or_page_output(value) || Pry::DEFAULT_PRINT.call(output, value)
end

Ches Martin over 13 years ago

Thank you! I took Pry for a spin several weeks ago but didn't take the time to fully explore getting Hirb working so I haven't been using it for Rails' console. I think I will now :-)

Ches Martin over 13 years ago

I added a dirty instance_eval hack to make Hirb.disable/enable work in-session:

https://gist.github.com/1177892

cldwalker is probably opinionated about Ripl, but I'll ask if he'll accept a patch to Hirb for built-in Pry support.

Edit: Just found this issue where he indeed says he doesn't want to support more shells in the gem itself (and you guys originally shared this .pryrc snippet =]).

Songrit Leemakdej over 13 years ago

I use binding.pry to break the app (start webrick with --debugger) but couldn't find how to step or next at the Pry prompt, though I can 'exit' to let the app continue. Is there anyway to have Pry work with ruby-debug?

John Mair over 13 years ago

A few options at present:

https://github.com/AndrewO/ruby-debug-pry

Also you may be interested in:

https://github.com/mon-ouie/pry_debug

Another thing i would like to do would be to bring ruby-debug commands into Pry itself, rather than having to use Pry from inside ruby-debug. This will be a task for the future (but should not be too difficult).

ajfre over 12 years ago

How to use pry_debug in a rake file?

Thomas Dippel over 13 years ago

Has anyone had any success with using the "binding.pry" feature with Pow?

John Mair about 13 years ago

try this and let me know how you get on: https://github.com/mon-ouie/pry-remote

railsman over 13 years ago

irb + rails debugger =pry...awesome.. makes life much easier..!

Enrico Carlesso over 13 years ago

Is there a way to use Pry with Foreman?

Michael over 12 years ago

check out https://github.com/mon-ouie/pry-remote
use binding.pry_remote in your code, and
and then from another terminal
pry-remote to connect

Potiguar Faga over 13 years ago

Yeah would be nice to run with Pow if possible. Any clues?

John Mair over 13 years ago

Hi, read the solution given in the following issue: https://github.com/pry/pry/issues/237

Let me know how you get on!

Potiguar Faga over 13 years ago

Hi John. It does work. Feels a bit hackish thou.

Also one thing I notice is that when using guard with rspec whenever I add a "binding.pry" line, the specs of course pause on that line. Would there be a way to avoid this? Well I guess I can always use...

binding.pry unless Rails.env.test?

John Mair over 13 years ago

It's hackish because it is a hack :) it's just a quick solution provided by a contributor to a specific issue -- remote sessions will be officially supported in a future version, but for now, this hack is ok, right? :)

I'm sorry i can't help you with your testing issue as i don't use RSpec :(

goodluck and i hope you like pry :)

Potiguar Faga over 13 years ago

cool cool! I get it's a temp hack, sorry to sound so eager. Really excited about it I guess. =) And yes, it does work for the time being.

Regarding my RSpec "issue", I guess it's more of a situation that everyone who runs any sort of autotest suite runs into.. the moment you insert a debug hook in the code, the automated tests kick in because you save the file, and they fire the hook.

I really do enjoy using Pry! thank you. =)

John Mair over 13 years ago

Looks like the pry-remote plugin may have been officially released now, try it and tell me if it's ok: https://github.com/mon-ouie/pry-remote

Kyle Heironimus over 13 years ago

Just tried the pry-remote plugin with pow, and so far it works great.

bbozo about 13 years ago

This is actually a feature, you can use binding.pry to troubleshoot why tests fail, I even did:

          ruby
        
class Test::Unit::TestCase
  alias_method :assert_block_without_pry, :assert_block

  def assert_block(message="assert_block failed.") # :yields: 
    begin
      assert_block_without_pry(message){ yield }
    rescue Exception => e
      binding.pry
      raise e
    end
  end
end

...but binding pry stopped working for me a week ago in tests, now it's throwing a NoMethodError: undefined methodactivate!' for nil:NilClass`

bbozo about 13 years ago

update: bundle update fixed binding.pry in tests

Bragaadeesh over 13 years ago

Thank you for such a wonderful screencast. Personally, I still feel the way may Rails developer debug their code is still elementary. Although you may be using debugger or even a Pry, it is still obtrusive, meaning you have directly insert lines into your code like debugger or binding.pry which is a very inefficient way.

Rails developers should start switching to IDEs already.

George Plymale almost 13 years ago

I have to agree with @EnricoCarlesso I would like to understand if there is a way to run Pry with Foreman. It seems that it works okay except you cannot see your input when running a web worker plus regular cron-esque worker. I set the unicorn web workers down to 1 so that it wouldn't conflict in that regard, but still the input is an issue.

Duncan Beevers almost 13 years ago

You can use the pry-rails gem to automatically use pry as the Rails console.

ajfre over 12 years ago

How to use pry_debug in a rake file?

Andy Zhang over 12 years ago

Great screencast! Could definitely benefit from an update that uses the pry-rails gem.

bachue over 12 years ago

I think it's not convenient to debug in action of rails, because there's no list, step, next method, while we can't call an action directly.

John Mair almost 12 years ago

use pry-debugger plugin

Douglas G. Allen almost 10 years ago

As a general question Ryan, do you rehearse these until you can get them in one session or do you do a lot of edits. Just curious.
Or maybe you are just that good at it?
Either way tanks! Oops! Do you have a screen-cast showing how to use the new Rails4 error console?

Download App about 7 years ago

why is this present here?