to_xml

Returns a string that represents the array in XML by invoking to_xml on each element. Active Record collections delegate their representation in XML to this method.

All elements are expected to respond to to_xml, if any of them does not then an exception is raised.

The root node reflects the class name of the first element in plural if all elements belong to the same type and that’s not Hash:

customer.projects.to_xml

<?xml version="1.0" encoding="UTF-8"?>
<projects type="array">
  <project>
    <amount type="decimal">20000.0</amount>
    <customer-id type="integer">1567</customer-id>
    <deal-date type="date">2008-04-09</deal-date>
    ...
  </project>
  <project>
    <amount type="decimal">57230.0</amount>
    <customer-id type="integer">1567</customer-id>
    <deal-date type="date">2008-04-15</deal-date>
    ...
  </project>
</projects>

Otherwise the root element is “records”:

[{:foo => 1, :bar => 2}, {:baz => 3}].to_xml

<?xml version="1.0" encoding="UTF-8"?>
<records type="array">
  <record>
    <bar type="integer">2</bar>
    <foo type="integer">1</foo>
  </record>
  <record>
    <baz type="integer">3</baz>
  </record>
</records>

If the collection is empty the root element is “nil-classes” by default:

[].to_xml

<?xml version="1.0" encoding="UTF-8"?>
<nil-classes type="array"/>

To ensure a meaningful root element use the :root option:

customer_with_no_projects.projects.to_xml(:root => "projects")

<?xml version="1.0" encoding="UTF-8"?>
<projects type="array"/>

By default name of the node for the children of root is root.singularize. You can change it with the :children option.

The options hash is passed downwards:

Message.all.to_xml(:skip_types => true)

<?xml version="1.0" encoding="UTF-8"?>
<messages>
  <message>
    <created-at>2008-03-07T09:58:18+01:00</created-at>
    <id>1</id>
    <name>1</name>
    <updated-at>2008-03-07T09:58:18+01:00</updated-at>
    <user-id>1</user-id>
  </message>
</messages>