Dive into Pry

This note was written for Ruby < 2.0, thus outdated now.

Input

• !: clear input buffer
• code;: suppress evaluation output, useful when it's long or uninterested.
• amend-line N replacement code: to amend lines of input. Use ! for replacement to delete. You can use show-input to get line numbers.
• .shellcommad #{ruby code}

Special locals

• _: last result
• _ex_: the most recently caught exception
• _in_ and _out_: Input expressions and output results are automatically stored in array-like data structures.
• _file_ and _dir_: last file and last directory
• _pry_: current Pry instance

Browsing code

Use cd to move into an object or scope. As in UNIX shells use cd .. to go back, cd / to return to Pry top-level and cd - to toggle between last two scopes. Complex syntax (e.g cd ../@x/@y) also supported.

Use whereami(alias @) to show code surrounding the current context.

Use show-source(alias $ or show-method) and show-code(alias ?).

Use find-method to recursively search for a method within a class/module or the current namespace.

Use stat method_name for basic method information.

Use ls to get a list of variables in current scope You can also use ls Class/Module, or ls variable.

Use watch to watch the value of an expression and print a notification whenever it changes.

cat automatic syntax highlighting for a number of file types.

cat accepts the following options:

• --[l]inenumbers causes line numbers to be displayed along side each line.
• --[t]ype: syntax highlight type
• --[s]tart and --[e]nd: the line of the file with which to begin/end
• --ex: last exception
• --in: one or more entries from Pry's expression history (default: -5..-1)

Editing code

edit brings you to EDITOR. It accepts the following options:

• -c: current file/line
• my_method: method in the scope
• Class#a_method or Class.a_class_method
• <filename> or <filename>:<line-number>
• --in 1..2: a range of the Pry input buffer
• -t: open a temporary empty file in an editor
• --ex: the relevant file at the line that generated the last exception
• --ex N: the Nth line of the backtrace
• -l: jump to the specified line number
• -n: stop the automatic reloading of .rb files after you have edited them
• -r: force Pry to reload and eval a file, even if it does not end in .rb

Being run without any arguments, the edit command modifies the last input expression.

History

hist to display Pry history.

It accepts the following options:

• --grep REGEX
• --exclude: when displaying history, exclude pry commands
• --tail N and --head N: N defaults to 10
• --no-numbers or -n: turns off line numbers when displaying history
• --show A..B
• --replay A..B: replay lines of history.
• --save [A..B] FILE: save to a file
• --clear: clear all current session history

Debug

Write binding.pry as a breakpoint in your code. When executing, it will stop here and open a Pry console.

Gems

• gem-cd Change working directory to specified gem's directory.
• gem-install Install a gem and refresh the gem cache.
• gem-list List and search installed gems.
• gem-open Opens the working directory of the gem in your editor.

Customization

For current session:

Pry.config.[option]

You can store Pry.config.[option] in .pryrc (project or global ~/.pryrc).

Plugins

pry-byebug

Use byebug (Ruby debugger) with pry.

I don't use it due to this bug. Besides, most of time, I just need pry-rescue.

pry-coolline

By default, code gets highlighted after you end your input. This plugin supports real time highlight.

pry-macro

Record and play macros. You can save macros to a file.

pry-rescue

Whenever an unhandled exception happens in your program, pry-rescue opens an interactive pry shell right at the point it was raised.

Install it together with pry-stack_explorer, then run rescue file.rb instead of ruby file.rb.

In the rescue Pry session, use up and down to move around the stack, and use wtf? or cat --ex to examine stack traces and the associated code. After identifying the problem, use edit-method (alias $) to fix the code, and try-again to verify the fix worked.

cd-cause lets you rewind back the previously raised exception. So, if you've rescued one exception, and then raised another (it happens…) you can jump back to the original cause of the problem.

You can also call Pry::rescue to control over which parts of your code are rescued:

 1require 'pry-rescue'
 2
 3def test
 4  raise "foo"
 5rescue => e
 6  raise "bar"
 7end
 8
 9Pry.rescue do
10  test
11end

You can also use Pry::rescue in the rescue clause:

1def test
2  raise "foo"
3rescue => e
4  Pry::rescued(e)
5end
6
7Pry::rescue{ test }

Testing

rspec

rescue rspec

MiniTest

Add the following to your test_helper.rb or to the top of your test file

1require 'minitest/autorun'
2require 'pry-rescue/minitest'

It works perfectly with yard-doctest in terminal, but not is sublime-text.

Themes

In a pry session, run pry-theme list to list all installed themes.

Try a theme:

pry-theme try pry-modern-256

If the theme is not installed, you can install it:

pry-theme install theme-name

You can use uninstall to uninstall it.

Show current theme:

pry-theme current

You can edit a theme:

pry-theme edit

After you have decided your theme, write it in .pryrc:

Pry.config.theme = "pry-modern-256"

You can get more themes at Pry theme collection.