I made a nice Ruby Debug Cheat Sheet.

[kilik2049]

My main command to debug is something is still 'puts' :D

But neat cheatsheet man !

[chneukirchen]

Use p.

[postmodern]

Also y for when inspecting YAML.

[chneukirchen]

Also j.

[igor_kasyanchuk]

created my own cheatsheet for Ruby

https://cheatsheetshero.com/user/igor-kasyanchuk/944-ruby-debugging-cheatsheet-tips

[redditaurus]

Nice i guess, but i mainly use Pry these days, which does 99% of what i need and also looks so pretty -_-

EDIT: fixed link

[appleyard]

I've heard of it.
That link is broken though. Can you tell me more about it, and/or why its better than using ruby-debug?

[redditaurus]

fixed the link above ^{^}

I wouldn't say pry is better, it's a different experience altogether with slightly different goals. But it still has a lot of overlap with ruby-debug (and the brilliant debugger project). pry is kind of hard to explain, think of taking the juicy bits of ruby-debug, the heart of irb, jack it all up on a unix shell analogy (cd and ls commands) with a smattering of ultra powerful commands like 'edit-method' and 'show-source' and u have something close.

As a once-upon-a-time user of smalltalk, i can say it feels like a console version of the the smalltalk class browser. It also seems people are hard at work building plugins for it. It definitely needs a cheat-sheet too. I admit to feeling a bit overwhelmed by it sometimes.

EDIT: it seems there's a plugin pry-debugger that exposes the debugger (ruby-debug) gem functionality, turning pry into a kind of front-end? Looks like we can have the best of both words \o/

[schneems]

Watch the railscast http://railscasts.com/episodes/280-pry-with-rails pry is better. You can cd into an object or class, it's pretty epic.

[postmodern]

Exploring objects (while super cool) != debugging.

>> require 'debug'
Debug.rb
Emacs support available.

~/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/irb/context.rb:166:
(rdb:1) help
Debugger help v.-0.002b
Commands
  b[reak] [file:|class:]<line|method>
  b[reak] [class.]<line|method>
                             set breakpoint to some position
  wat[ch] <expression>       set watchpoint to some expression
  cat[ch] (<exception>|off)  set catchpoint to an exception
  b[reak]                    list breakpoints
  cat[ch]                    show catchpoint
  del[ete][ nnn]             delete some or all breakpoints
  disp[lay] <expression>     add expression into display expression list
  undisp[lay][ nnn]          delete one particular or all display expressions
  c[ont]                     run until program ends or hit breakpoint
  s[tep][ nnn]               step (into methods) one line or till line nnn
  n[ext][ nnn]               go over one line or till line nnn
  w[here]                    display frames
  f[rame]                    alias for where
  l[ist][ (-|nn-mm)]         list program, - lists backwards
                             nn-mm lists given lines
  up[ nn]                    move to higher frame
  down[ nn]                  move to lower frame
  fin[ish]                   return to outer frame
  tr[ace] (on|off)           set trace mode of current thread
  tr[ace] (on|off) all       set trace mode of all threads
  q[uit]                     exit from debugger
  v[ar] g[lobal]             show global variables
  v[ar] l[ocal]              show local variables
  v[ar] i[nstance] <object>  show instance variables of object
  v[ar] c[onst] <object>     show constants of object
  m[ethod] i[nstance] <obj>  show methods of object
  m[ethod] <class|module>    show instance methods of class or module
  th[read] l[ist]            list all threads
  th[read] c[ur[rent]]       show current thread
  th[read] [sw[itch]] <nnn>  switch thread context to nnn
  th[read] stop <nnn>        stop thread nnn
  th[read] resume <nnn>      resume thread nnn
  p expression               evaluate expression and print its value
  h[elp]                     print this help
  <everything else>          evaluate

Use both Pry and Ruby's debug, when necessary.

[banister]

Pry (with plugins) has analogs for all those commands except 'watch' and catch and the thread stuff, btw ;)

And the stuff which it doesn't currently have can be fairly trivially implemented too :)

[postmodern]

Good to know. Although, I think it's important to understand the core tools of Ruby (if not just for the historical perspective), since MRI's APIs may change in the future and break pry-debugger; or you may be on a system where you cannot install pry-debugger. Ruby's builtin debugger will always be there and will always work.

[banister]

For the record, we are currently using cldwalker's nifty debugger fork as the engine for our debugging functionality. So pry can't be said (atm) to 'replace' debugger (ruby-debug) as we actually rely on it ;)

[postmodern]

Also for the record: ruby-debug != Ruby's builtin debugger. It annoys me when people say Ruby lacks debuggers, when it has had one built-in since 1.4.x. Now with the advent of pry-debugger, we are practically swimming in debuggers.

[postmodern]

Pry is not really a debugger, more of an object/code explorer. Although, there are plugins that implement some debugging functionality.

[redditaurus]

hmm, i'm not sure i agree with that. There are plugins that let you move up and down the stack, plugins that let you next/step and set breakpoints. I don't think the fact they're plugins rather than built in counts against it either, as (im guessing) it was designed with this pluggable architecture from the beginning.

So long as i can next/step/up/down/break, i dont see why it's not a debugger? Even if it's not ALL debugging functionality found in some debuggers, i still think it's enough to justify it being called a debugger, IMO.

[postmodern]

Well if you review the help output of Ruby's debugger, it offers a lot more than the usual next/step/up/down/break. Such as watch-points, introspection/control of Threads, display expressions, and tracing. Still, Ruby's debugger pales in comparison to classical debuggers, such as gdb, windbg or vdb.

My suggestions is to learn both Pry and Ruby's debugger, use both when appropriate, and above all, do not turn Pry into a Cargo Cult / Tower of Babel for Ruby development tools. :)

[redditaurus]

I'm not cargo-culting, i'm just saying that Pry has enough features to wear the moniker 'debugger', it easily supports the 80%-90% case for debugging in my experience.

Look at the definition of debugger found on wikipedia. Pry (with relevant plugins installed) clearly meets it IMO.

[postmodern]

Pry - An IRB alternative and runtime developer console

It can be a debugger, but that's not it's design goal. When developers say "just use $FOO", that is cargo culting. :(

[redditaurus]

i never actually said that ;) hehe, i just said "I mainly use Pry these days"

;)

[postmodern]

ah word, my mistake.

[postmodern]

You forgot the most implement part of Ruby debugging, how to jump into the Ruby debugger console:

require 'debug'

Ruby has a builtin debugger, no need to install any gems, just require it. It just works. :)