How to add interactive console to your Ruby app?

I’ve been writing some Ruby app lately (the kind that runs in the terminal and doesn’t include Webrick as http server) and I found myself missing some of the tooling that is available with Rails - especially the command line. The ability to just type rails c and play around with your code was one of the framework killer-features back in the days:

Here’s how to do it in Ruby console application :)

Sample application

Our app will contain only three files

# cat.rb
class Cat
  def make_sound
    puts 'miau' 
  end
end

# config/application.rb
require_relative '../cat'

# main.rb
require_relative 'config/application'
Cat.new.make_sound

Console script

We will follow Rails conventions and put our executables in the bin directory

# bin/console

#!/usr/bin/env ruby
require 'irb'
require 'irb/completion'
require_relative '../config/application'

IRB.start

And that’s it - we can now type bin/console and our Cat class is available!

Reloading code

It wouldn’t feel like a real console without being able to call reload! so let’s try to add it!

First we need to change require to load in application.rb because the former will not load our source file again if it has been already loaded.

# config/application.rb
load File.expand_path('../../cat.rb', __FILE__)

And then we will add reload! function to our script:

# bin/console

#!/usr/bin/env ruby
require 'irb'
require 'irb/completion'

def reload!
  load File.expand_path('../../config/application.rb', __FILE__)
end

reload!
IRB.start