Nokogiri XML builder with attributes and no xml declaration

after.rb

require 'nokogiri'

def common_code_for_element_recipients(numbers)
  xml = Nokogiri::XML::Builder.new
  xml.recipients do
    numbers.each do |number|
      if number.is_a? Hash
        xml.recipient(uid: number[:uid]) { xml.text number[:uid] }
      else
        xml.recipient number
      end
    end
  end
  xml.doc.root.to_xml
end

puts common_code_for_element_recipients([{uid: '123456789'}, '987654321'])

before.rb

    def common_code_for_element_recipients(numbers)
      recipients_body_xml = '<recipients>'
      numbers.each do |number|
        # start the XML block
        recipients_body_xml += "\n    <recipient"
        # individual numbers and (optional) UIDs
        if number.is_a? Hash
          recipients_body_xml += " uid=\"#{number[:uid]}\""
          number = number[:number]
        end
        recipients_body_xml += ">#{number}</recipient>"
      end
      # close XML block
      recipients_body_xml += "\n  </recipients>"
    end