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 i

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).