Customize Your IRB

You probably spend a lot of time in IRB (or the Rails console) but have you taken the time to customize it? Today we’ll take a look at the things I’ve added to mine, and I’ll show you how to hack in a .irbrc_rails that’s only loaded in the Rails console.

# ruby 1.8.7 compatible
require 'rubygems'
require 'irb/completion'

# interactive editor: use vim from within irb
begin
  require 'interactive_editor'
rescue LoadError => err
  warn "Couldn't load interactive_editor: #{err}"
end

# awesome print
begin
  require 'awesome_print'
  AwesomePrint.irb!
rescue LoadError => err
  warn "Couldn't load awesome_print: #{err}"
end

# configure irb
IRB.conf[:PROMPT_MODE] = :SIMPLE

# irb history
IRB.conf[:EVAL_HISTORY] = 1000
IRB.conf[:SAVE_HISTORY] = 1000
IRB.conf[:HISTORY_FILE] = File::expand_path("~/.irbhistory")

# load .irbrc_rails in rails environments
railsrc_path = File.expand_path('~/.irbrc_rails')
if ( ENV['RAILS_ENV'] || defined? Rails ) && File.exist?( railsrc_path )
  begin
    load railsrc_path
  rescue Exception
    warn "Could not load: #{ railsrc_path } because of #{$!.message}"
  end
end

class Object
  def interesting_methods
    case self.class
    when Class
      self.public_methods.sort - Object.public_methods
    when Module
      self.public_methods.sort - Module.public_methods
    else
      self.public_methods.sort - Object.new.public_methods
    end
  end
end

Ok! There’s not too much there, but let’s break it down from top to bottom.

Require commonly used gems

# ruby 1.8.7 compatible
require 'rubygems'
require 'irb/completion'

# interactive editor: use vim from within irb
begin
  require 'interactive_editor'
rescue LoadError => err
  warn "Couldn't load interactive_editor: #{err}"
end

# awesome print
begin
  require 'awesome_print'
  AwesomePrint.irb!
rescue LoadError => err
  warn "Couldn't load awesome_print: #{err}"
end

Nothing too fancy here. Just some require commands and initialization to load up some of my favorite and frequently used gems.

• interactive_editor: Allows you to use vim (or your favorite editor) to edit files and have them run within the context of the irb session and to edit objects’ YAML representation.
• Awesome Print: Pretty prints Ruby objects in color and with nice formatting to show their structure. Seriously useful if you inspect a lot of data. The .irb! call hooks it into irb as the default formatter so you don’t even need to call it directly. It just happens.

Configure the prompt and add history

# configure irb
IRB.conf[:PROMPT_MODE] = :SIMPLE

# irb history
ARGV.concat [ "--readline", "--prompt-mode", "simple" ]
IRB.conf[:EVAL_HISTORY] = 1000
IRB.conf[:SAVE_HISTORY] = 1000
IRB.conf[:HISTORY_FILE] = File::expand_path("~/.irbhistory")

Prompt mode simple just makes prompts look like >> instead of 1.9.3p327 :001 >

Command history is obviously supremely useful if you frequently use the console to hack out solutions.

Optionally load customizations for the Rails console

# load .irbrc_rails in rails environments
railsrc_path = File.expand_path('~/.irbrc_rails')
if ( ENV['RAILS_ENV'] || defined? Rails ) && File.exist?( railsrc_path )
  begin
    load railsrc_path
  rescue Exception
    warn "Could not load: #{ railsrc_path } because of #{$!.message}"
  end
end

Ahh, now things get interesting. If we detect RAILS_ENV or the Rails object is defined then we can assume that we’re actually inside a Rails console and add some extra configuration. We’ll get to that extra configuration for Rails in a moment.

Add .interesting_methods

class Object
  def interesting_methods
    case self.class
    when Class
      self.public_methods.sort - Object.public_methods
    when Module
      self.public_methods.sort - Module.public_methods
    else
      self.public_methods.sort - Object.new.public_methods
    end
  end
end

This one is pretty fun. It adds on a method to Object called interesting_methods. Ruby’s object model is great, but it means that the public api to any object is full of methods defined up its ancestor chain.

>> Object.new.methods.count
71
>> Module.new.methods.count
111
>> Class.new.methods.count
115

interesting_methods gives us an easy way to filter all that out.

class Magic
  def cast
    'poof'
  end
end

>> Magic.new.methods.count
72
>> Magic.new.interesting_methods.count
1
>> Magic.new.interesting_methods
[
  [0] :cast
]

Handy! And with some introspection that code accounts for module and class methods as well.

Rails customizations

Loading an rc file just for the Rails console adds all kinds of opportunities for enhancement.

# hirb: some nice stuff for Rails
begin
  require 'hirb'
  HIRB_LOADED = true
rescue LoadError
  HIRB_LOADED = false
end

require 'logger'

def loud_logger
  enable_hirb
  set_logger_to Logger.new(STDOUT)
end

def quiet_logger
  disable_hirb
  set_logger_to nil
end

def set_logger_to(logger)
  ActiveRecord::Base.logger = logger
  ActiveRecord::Base.clear_reloadable_connections!
end

def enable_hirb
  if HIRB_LOADED
    Hirb::Formatter.dynamic_config['ActiveRecord::Base']
    Hirb.enable
  else
    puts "hirb is not loaded"
  end
end

def disable_hirb
  if HIRB_LOADED
    Hirb.disable
  else
    puts "hirb is not loaded"
  end
end

def efind(email)
  User.find_by_email email
end

# set a nice prompt
rails_root = File.basename(Dir.pwd)
IRB.conf[:PROMPT] ||= {}
IRB.conf[:PROMPT][:RAILS] = {
  :PROMPT_I => "#{rails_root}> ", # normal prompt
  :PROMPT_S => "#{rails_root}* ", # prompt when continuing a string
  :PROMPT_C => "#{rails_root}? ", # prompt when continuing a statement
  :RETURN   => "=> %s\n"          # prefixes output
}
IRB.conf[:PROMPT_MODE] = :RAILS

# turn on the loud logging by default
IRB.conf[:IRB_RC] = Proc.new { loud_logger }

Note, for these enhancements to work in Rails apps that use bundler you’ll need to add the required gems to your Gemfile and then run bundle.

group :development do
  gem "awesome_print"
  gem "hirb"
  gem "interactive_editor"
end

Hirb is an awesome thing to add to your Rails console. It adds stuff like table formatting for models and general data, a console menu, and a pager.

The logger customizations will output things like SQL statements made to the database unless quiet_logger is called. Very handy if you are debugging a complex ActiveRecord query.

The prompt mode configuration is just a nice prompt with the application name. We define a :RAILS prompt mode and then use it.

That efind method is just a handy shortcut for something I do semi-often. It combines well with a dash expander shortcut that autofills in my email address.

Want to know more?

There’s a great post on tagholic with tons of info on how to completely customize your irb session: Exploring how to configure irb. If you’re interested in any of the options I use in this post, odds are good that they are explained in much more detail there.