Drupal Migrate - Link fields from an XML Source
So, the solution is to not use arguments, but instead, fix up the record using the prepare() method:

In the constructor:

//IMPORTANT - DO this source mapping without a destination mapping (NULL)
$this-&gt;addFieldMapping(NULL, 'organization_title')-&gt;xpath('/record/organization/title');

$this-&gt;addFieldMapping('field_organization', 'organization_url')-&gt;xpath('/record/organization/url');


Then, create a method named prepare():

function prepare($node, $rec) {
      $node-&gt;field_organization[LANGUAGE_NONE][0]['title'] = $rec-&gt;organization_title;
}


As of today (Nov 30, 2011), you must have the 7.x-dev version of the link module installed, not the "stable" 1.0 version, in order for link fields to work at all!

Whew!