Returns all classes that have (a class) in their subclass/ancestor chain

subclasses_of.rb

class Base; end;
class Parent < Base; end
class Grandchild < Parent; end

def subclasses_of(a_class)
  classes = []
  ObjectSpace.each_object(Class) do |klass|
    decendents = []

    current_class = klass
    while true do
      superc = current_class.superclass
      break if superc.nil?
      decendents << superc
      current_class = superc
    end

    if decendents.include? a_class
      classes << klass
    end
  end

  classes
end

things = subclasses_of(Base)  # or umm ActiveRecord::Base ;)
puts things