I needed to be able to find out what modules were defined inside a particular ruby module. Kinda like wanting to find out what child namespaces exist for a module. It’s probably more easily explained with an example. Given the following construct…

module A
  module B; end
  module C; end
  module D
    module E; end
  end
end

…I wanted to be able to ask A what submodules are defined within it and get the following answer:

[A::B, A::C, A::D]

(btw: I don’t want to see E in the list as it is not a direct child of A).

So… since the Module class doesn’t provide anything to support doing that, I wrote a method that does it for me. Here’s the monkey-patch:

class Module
  def submodules
    constants.collect {|const_name| const_get(const_name)}.select {|const| const.class == Module}
  end
end

With that, you can now call the submodules method against any module and you’ll be returned an array of modules!