There are different ways to create recursive hash in ruby. I found two tricks from here: http://metaskills.net/2012/03/12/store-configurable-a-lesson-in-recursion-in-ruby/

gistfile1.rb

# ruby recursive hash examples
# http://metaskills.net/2012/03/12/store-configurable-a-lesson-in-recursion-in-ruby/

# trick 1
class RecursiveHash < Hash
  Recursive = lambda { |h,k| h[k] = h.class.new }
  def initialize
    super(&Recursive)
  end
end

hash = RecursiveHash.new  # => {}
hash.class                # => RecursiveHash
hash[:foo]                # => {}
hash[:foo].class          # => RecursiveHash
hash[:a][:b][:c]          # => {}
hash                      # => {:foo=>{}, :a=>{:b=>{:c=>{}}}}

loader = lambda do |hash, key, value|
  if value.is_a?(Hash)
    value.each { |k,v| loader.call(hash.send(key), k, v) }
  else
    options.send "#{key}=", value
  end
end

data.each { |k,v| loader.call(config, k, v) }

#trick 2
my_hash = Hash.new { |h, k| h[k] = Hash.new(&my_hash.default_proc) }