Generating a Class Hierarchy in Ruby

May 2013 · less than 1 minute to read

Here’s a way to see what classes descend from a particular superclass in Ruby. You can use it to list all ActiveRecord models defined in your application, every implementation on a particular base class, or whatever else might be of interest.

> puts ClassHierarchy.new ActionController::Base
ActionController::Base
  ApplicationController
    UsersController
    UserSessionsController
    OrdersController
    ...

If you’re using Rails, bear in mind that most of your classes won’t be loaded by default in the development environment. You can get around this by manually requiring the files you’re interested in:

Dir.glob File.join(Rails.root, 'app/models/**/*.rb'), &method(:require)

To use in your code, simply put class_hierarchy.rb somewhere that makes sense (perhaps /lib) and require 'class_hierarchy'.