ActiveSupport、Hash#to_xml

everyday Ruby 
>> require "rubygems"
=> true
>> require "active_support"
=> true
>> Hash.from_xml([{:foo => 1, :bar => 2}, {:baz => 3}].to_xml).to_xml
=> "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<hash>\n  <records type=\"array\">\n    <record>\n      <foo type=\"integer\">1</foo>\n      <bar type=\"integer\">2</bar>\n    </record>\n    <record>\n      <baz type=\"integer\">3</baz>\n    </record>\n  </records>\n</hash>\n"