symfony render a template/partial in a form

I am trying to render a template in a form using the _toString() method. The problem I am facing is that the form does not inherit from controller and I can not do $str.= $this->renderPartial('template',array('form' => $this)); How can this be achieved ?

I am using symfony 1.4 with PHP 5.3

You can create a widget for it:

class fdWidgetFromPartial extends sfWidgetForm
{
  public function __construct($options = array(), $attributes = array())
  {
    parent::__construct($options, $attributes);

    sfProjectConfiguration::getActive()->loadHelpers('Partial');
  }

  protected function configure($options = array(), $attributes = array())
  {
    $this->addRequiredOption('template');
    $this->addOption('variables', array());
  }

  public function render($name, $value = null, $attributes = array(), $errors = array())
  {
    return get_partial($this->getOption('template'), array_merge(array(
      'name' => $name,
      'value' => $value,
      'attributes' => $attributes,
      'errors' => $errors,
    ), $this->getOption('variables')));
  }
}

And use it like this:

$this->setWidget('field', new WidgetFromPartial(array(
  'template' => 'modeule/template',
  'variables' => array(
    'some_data' => $this->getObject()->getData(),
  )
)));

You should NOT use any input field in the partial.