This document is a presentation on debugging Ruby applications. It discusses various debugging techniques like stack traces, logging, and the debug and ruby-debug modules. It focuses on the ruby-debug and Pry debugging tools, demonstrating their features. It emphasizes that while test-driven development prevents many bugs, debugging is still important to understand legacy code, untested code, or unexpected behavior. The presentation concludes by discussing the speaker's experience with the Ruby community in Brazil.

1. The ultimate
guide to ruby
debugging
Rafael Rosa Fu
March 2012 - Montreal.rb
@rafaelrosafu

2. The ultimate
guide to ruby
debugging
Rafael Rosa Fu
March 2012 - Montreal.rb
@rafaelrosafu

3. Ruby debugging
basics
Rafael Rosa Fu
March 2012 - Montreal.rb
@rafaelrosafu

4. About me
More on that later

5. Why?
● TDD won't save you all the time
● Understand untested, legacy, complicated
code
● Understand unexpected behavior
● Interactive coding

6. Why?
● "When I coded in Delphi 2 I had support for it
on my IDE"

7. How?
●
●
●
●
Stack traces
puts, p, pp
Logging
debug module
● ruby-debug
○ ruby-debug19
● Pry
○ pry-nav
○ pry-stack_explorer

8. How?
●
●
●
●
Stack traces
puts, p, pp
Logging
debug module
● ruby-debug
○ ruby-debug19
● Pry
○ pry-nav
○ pry-stack_explorer

9. ruby-debug
Created by Kent Sibilev and Rocky Bernstein
● https://github.com/ruby-debug/ruby-debug
● http://bashdb.sourceforge.net/ruby-debug.
html
ruby-debug19 is a port by Mark Moseley

10. ruby-debug for 1.8.7
1. gem install ruby-debug
2. profit

11. ruby-debug for 1.9.x
1. gem install ruby-debug19
2. profit (almost)
● Workaround for 1.9.3:
○ Need newer versions for linecache and ruby-debugbase, not on rubygems
○ Some stuff is still broken
○ https://gist.github.com/2047760
○ Thanks to @fredostarr, @spastorino, @rafaeldx7
and @garyharan

12. ruby-debug
●
●
●
●
●
●
Follow the code execution
Inspect objects
Set breakpoints
See the stack
Change state (be careful)
Debug remotely

13. ruby-debug demo
● Lots of commands
○
○
○
○
○
○
●
debugger, rdebug
list, help, quit
p, pp, ps, display, info
break, next, step, continue
disable, condition
irb, where, edit, set, show
Fingers crossed

14. ruby-debug demo
Live demos always go wrong
Sorry in advance :)

15. Pry

16. Pry
● Developed by John Mair (@banisterfiend)
● http://github.com/pry/pry
● Started as a turbo irb
● An ecosystem is growing around it
○ Lots of plugins

17. Pry
● gem install pry
● gem install pry-doc

18. Pry demo
● Nice features
○
○
○
○
pagination
autocomplete
syntax highlight
highly customizable
● Lots of commands and features
○
○
○
○
●
●
ls, ls --help
cd, nesting, exit
.commands
show-doc, show-method, edit-method
pry-nav is not ready for primetime
pry-stack_explorer is ok

19. Lessons learned
● Debugging is not a bad thing when used
properly and sparingly
● Basic tools solve ~ 90% of the issues
● BDD/TDD will save you from debugging
most of the time
● The future is quite cloudy for Ruby debug
tools:
○ https://github.com/rocky/rb-trepanning
○ Cross-implementation?
○ http://blog.bithug.org/2011/09/maglev-debug

20. References - ruby-debug
● http://bashdb.sourceforge.net/ruby-debug.html
● http://railscasts.com/episodes/54-debugging-with-ruby●
●
●
●
debug
http://guides.rubyonrails.
org/debugging_rails_applications.html
https://github.com/ruby-debug
https://github.com/mark-moseley/ruby-debug/
https://gist.github.com/2047760

21. References - Pry
● http://pry.github.com
● https://github.com/pry
● http://banisterfiend.wordpress.com/2012/02/14/the-pry●
●
●
ecosystem/
http://pry.github.com/screencasts.html
○ Special thanks to @fnando :)
http://railscasts.com/episodes/280-pry-with-rails
http://twitter.com/banisterfiend

22. Questions
?
I just need 5 more minutes after this :)

23. About me
http://flagwallpapers.com/water-color-brazilian-

24. About me
● Coding professionally for 16 years
● Agilist, product and community guy too
● I love Ruby
"Ruby is designed to make programmers
happy"
- Matz

25. About me

26. About me

27. Ruby community in Brazil
40 to 60 people every month

28. Ruby community in Brazil
https://picasaweb.google.com/105291946909431816672

29. Ruby community in Brazil
https://picasaweb.google.com/105291946909431816672

30. Ruby community in Brazil
http://groups.google.com/group/dojo_sp

31. Ruby community in Brazil
http://pothix.com/blog/events/encontro-de-numero-5-do-guru-

32. Ruby community in Brazil
http://blog.lambda3.com.br/2012/02/dojo-dojo-

33. Ruby community in Brazil
~ 1,500 attendees, this year will be the 5th edition
http://www.flickr.

34. Ruby community in Brazil
~ 1,500 attendees, this year will be the 5th edition
http://www.flickr.

35. Ruby community in Brazil
Everybody is invited - August 30 and 31 2012 - São Paulo
http://www.flickr.

36. Thank you
Merci :)
@rafaelrosafu
rrosa@iweb.com
rafaelrosafu@gmail.com
grokpodcast.com
linkedin.com/in/rafaelrosafu