Pry

• ls classname - shows methods
• _ - last value output
• ? classname.methodname - shows doc for method
• $ classname.methodname - shows source for method
• cat filename - output file
• file - last file touched
• wtf? - show backtrace for last error
• edit classname.methodname - opens in editor
• edit –ex - edit where most recent exception happened
• binding.pry - add into your app code to do a break point
• . - run rest of line as a shell command
• ; - put at end of line to not show return value, like if you only want output, or if you get back a huge object

Debugging

• play -l linenum - execute the code on a certain line
• cd varname - changes the value of self
• cd .. - go out a level
• whereami - where did the debugger stop
• ls - shows methods, instance variables, and locals

pry-debugger

• step - step into method
• next
• continue

pry-rescue

break on unhandled exception

• cd-cause - go to where exception thrown
• try-again - replays Rails request

pry-stack_explorer

• show-stack — shows stack trace
• up, down — move up and down the stack

pry-clipboard

• copy-history — copies a command history entry

Videos

• Pry—The Good Parts! (video)
• Debugger-Driven Development with Pry

Ruby’s dynamic nature allows this kind of real-time introspection and changes