Joomla Custom Content Not Saving - joomla

Question

I have written a simple plugin to include custom content against Joomla articles. Here's the code:
defined ( '_JEXEC' ) or die ( 'Restricted access' );
class plgContentHomegrid extends JPlugin {
protected $autoloadLanguage = true;
function onContentPrepareForm($form, $data) {
$app = JFactory::getApplication();
$option = $app->input->get('option');
switch($option) {
case 'com_content':
if ($app->isAdmin()) {
JForm::addFormPath(__DIR__ . '/forms');
$form->loadFile('homegrid', false);
}
return true;
}
return true;
}
}
This works fine, the additional fields are displayed as a separate tab in admin, data saves correctly and everything's perfect. So far so good...however, I only want to display the additional tab on the home page. So, I amended the code so the additional form is only displayed for the home page:
if( $data->featured == 1 ){
$form->loadFile('homegrid', false);
}
The form now only displays on the home page admin screen as needed BUT the data is not saved.
What am I doing wrong?

Answer 1

OK, the problem comes because my conditional references the $data item, which is not populated during save, just display (as recorded here)
So, a little investigation finds this solution works fine:
if( $data->featured == 1 || $_POST['jform']['featured'] == 1 ){
$form->loadFile('homegrid', false);
}
There seems to be no documentation anywhere on this!!