Debugging Ruby or: How I Learned To Stop Putsing And Love Pry The talk I gave at BostonRB (http://bostonrb.org/) for October 3013

1. Or:
How
I
Learned
To
Stop
Putsing
And
Love
Pry
DEBUGGING RUBY

2. ABOUT ME
Luke Bergen
Twitter: @lbergen
Reviewed.com

3. Developers spend 60% of their time
debugging
puts doesn‟t always do the trick
Enter pry and friends
DEBUGGING IN RUBY

4. “An IRB alternative and runtime
developer console” - http://pryrepl.org
Three major pieces
Pry-core
Pry-custom
Pry-ecosystem
WHAT IS PRY?

5. Commands are the primary way of
interacting with Pry
Higher order of precedence than ruby code
Expandable
Regex based
PRY-CORE

6. binding.pry
play
wtf
whereami
? (show-doc)
$ (show-source)
edit
COMMANDS
ls
cd
amend-line
Also !s/foo/bar
.<shell_command>
exit

7. _
_pry_
_ex_
_in_
_out_
_file_
_dir_
SPECIAL LOCALS
Result of last line
Local pry instance
Last exception
Array of all ruby input expressions
Array of all ruby output results
Last referenced file
Last referenced directory

8. Pry can be configured by a .pryrc file
~/.pryrc
./.pryrc
Project level pryrc files are especially useful
when paired with custom commands
PRY-CUSTOM

9. Almost everything in pry is configurable
Some configuration can even be
modified at runtime via _pry_.<config>
Of particular importance/interest:
Editor
Command prefix
Custom commands
BASIC CUSTOMIZATIONS

10. When using „edit‟ pry uses this setting
If editor is not set, Pry defaults to nano
You can set editor to a proc which
accepts 2 params: file and line
E.g. for sublime text:
EDITOR

11. COMMAND PREFIX
A problem and a solution

12. COMMAND PREFIX
A more permanent solution
Pry.config.command_prefix = „%‟
Now all pry commands must be prefixed
with „%‟

13. CUSTOM COMMANDS
Pry also allows you to define your own
custom commands
By block or class
Useful for often repeated code that
shouldn‟t be checked in

14. CUSTOM COMMANDS
Suppose you need to clean your
database from time to time

15. CUSTOM COMMANDS
Programmers are lazy (in a good way)
We like our code DRY and expressive
Where is that laziness when it comes to
the console?
Pry + custom commands = DRY,
expressive console

16. Any gem whose name fits the format pry-
<plugin> is a plugin
Beware: these gems are auto-loaded by
pry
--no-plugins option will skip auto-loading
.pryrc files get loaded before plugins
Plugin specific suppression:
Pry.plugins[“debugger”].disable!
PRY-ECOSYSTEM (PLUGINS)

17. Pry-debugger
Works only in MRI 1.8 – 1.9
Pry-byebug
A fork of pry-debugger
Works in MRI 2.0 – 2.1
Pry-nav
Pure ruby implementation
Works on all rubies
DEBUGGERS

18. Pry-stack-explorer
Gives pry commands: up, down, frame, and show-
stack
Pry-rescue (Pry-exception_explorer has been
deprecated)
Allows you to rescue from exceptions into a pry
session
Rescue for entire program, or only for specified
blocks
Plymouth
Jump into a pry session on test failure
WHEN THINGS BREAK

19. Uses regex magic to add some easy-access
syntax hackery
Accessing instance variables
foo.@instance_var
Calling private methods
foo.!private_meth()
Examining things in parent pry sessions
puts ../local_var
Just be careful with your regexes
PRY-SYNTAX-HACKS

20. Pry-doc
Adds core ruby class documentation for “?” and
“$” commands
Pry-vterm_aliases
Makes your ZSH and Bash aliases available to
pry‟s .<shell> command
Pry-theme
Color themes for pry‟s syntax highlighting
MISCELLANEOUS PLUGINS

21. Pry-rails
Turns rails console into a pry session
Teaches Pry new commands
show-[middleware|model|models|route]
recognize-path
Pry-plus
A pre-packaged group of useful plugins
INTEGRATION

22. Puts is ok. But don‟t hesitate to drop back and
use the big guns
REPL driven programming is incredibly powerful
Especially when working with new code/library
Explore code
Bundle open your favorite gem when it bugs out (or
just cd into it)
You never know what you‟ll find
CONCLUSION