$this->SwiftMailer->viewBody('confirm'); // defaults to 'both'
$this->SwiftMailer->viewBody('confirm','plain');
$this->SwiftMailer->viewBody('confirm','html');

$html_plain = $this->SwiftMailer->viewBody('confirm','plain',true);
$html_body  = $this->SwiftMailer->viewBody('confirm','html',true);
// $both_body will contain an array of both the 'plain' and 'html' versions, in this order.
$both_body = $this->SwiftMailer->viewBody('confirm','both',true);