recsorthash.rb

module CoreExtensions
  module Hash
    module AdvancedManipulations
      # adapted from http://dan.doezema.com/2012/04/recursively-sort-ruby-hash-by-key/
      def recursively_sort_by_key(&block)
        self.keys.sort(&block).reduce({}) do |seed,key|
          seed[key] = self[key]
          if seed[key].is_a?(Hash)
            # why does it never get here?
            seed[key] = seed[key].recursively_sort_by_key(&block)
          end
          seed
        end
      end
    end
  end
end

Hash.include CoreExtensions::Hash::AdvancedManipulations
h = {peter: {lisa: 1, mary: 2, anja: 4, frank: 3}, klaus: 0}
pp h.recursively_sort_by_key # keys are not sorted because #is_a?(Hash) above never became true...
                             # it checks _sub_classes, not _immediate_ classes, alright, but where
                             # is there any subclassing going on here?