How do you find all modules and classes within a module, recursively?

Question

If you have:

module A
  class B
  end
end

You can find B and similar classes via A.constants. However, in Ruby 1.9.3, you cannot get B if it is within another module. In Ruby 1.8.7 you can.

module A
  module Aa
    class B
    end
  end
end

How do you get B from the first level of A? What I would like as output is an array of constants, which include all classes like B, but anywhere within the module A.

Answer 1

class Module
  def all_the_modules
    [self] + constants.map {|const| const_get(const) }
      .select {|const| const.is_a? Module }
      .flat_map {|const| const.all_the_modules }
  end
end

A.all_the_modules
# => [A, A::Aa, A::Aa::B]

This code will break if you do have circular namespaces, aka A::Aa::B.const_set(:A, A).