Ruby: iterate through nested object and replace keys (convert to symbol)

keys_to_sym.rb

# Convert all Hash keys to lowercase symbols
# @param obj [Object] any Ruby object
def keys_to_sym(obj)
  case obj
  when Array
    obj.each do |v|
      keys_to_sym(v)
    end
  when Hash
    obj.keys.each do |k|
      if k.class == String
        obj[k.downcase.to_sym] = keys_to_sym(obj.delete(k))
      end
    end
  end
  return obj
end