Rails array to_xml

I have an array of user objects which I want to return as xml. How can I use to_xml to include attributes on the root element? For example

    <users total="10">
      <user>开发者_运维百科;
      ..
      </user>
    </users>

I know you can add custom elements and attributes to the xml using a block with the to_xml method, but I'm not sure how to add to the root element. Maybe there's another way other than using to_xml

I have used xml builder. Following code snippet covers some tricky xml building.

In you controller,

require 'builder'

def show_xml
  @xml = get_xml_data
  respond_to do |format|
    format.html # show.html.erb
    format.xml { render :xml => @xml }
  end
end

def get_xml_data
  xml = Builder::XmlMarkup.new#(:target=>$stdout, :indent=>2)
  xml.instruct! :xml, :version => "1.0", :encoding => "US-ASCII"
  xml.declare! :DOCTYPE, :html, :PUBLIC, "-//W3C//DTD XHTML 1.0 Strict//EN",  
  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"
  favorites = {
    'candy' => 'Neccos', 'novel' => 'Empire of the Sun', 'holiday' => 'Easter'
  }

  xml.favorites do
    favorites.each do | name, choice |
     xml.favorite( choice, :item => name )
    end
  end
end