TYPO3 Extbase repository constraint with MM relation - model-view-controller

Question

I build an extension with a table for items, these can be either projects or objects, a project being a container for multple objects.
To distinguish, a checkbox is used to label an item as project, and when this checkbox is ticked an optional field is displayed.
This field is a relation (m:n) from the project to the objects it contains (same table). The Multiple side by side select displayes only non projects and objects not yet assigned to a project through foreign_table_where.
This field has following TCA:
'objects' => [
'displayCond' => 'FIELD:isproject:=:1',
'exclude' => 0,
'label' => $ll . 'tx_myext_domain_model_item.objects',
'config' => [
'type' => 'select',
'renderType' => 'selectMultipleSideBySide',
'foreign_table' => 'tx_myext_domain_model_item',
'foreign_table_where' => 'AND isproject = 0 AND tx_myext_domain_model_item.uid NOT IN (SELECT uid_foreign FROM tx_myext_item_object_mm WHERE uid_local != ###THIS_UID###)',
'MM' => 'tx_myext_item_object_mm',
'size' => 10,
'autoSizeMax' => 30,
'maxitems' => 9999,
'multiple' => 0
],
],
with my plugin I give the option (trough a flexform) to select to display only objects, only projects or both, done with following code in the repository:
public function findList($entryInclude = 'objects_only') {
/** #var \TYPO3\CMS\Extbase\Persistence\Generic\Query $query */
$query = $this->createQuery();
switch ($entryInclude) {
case 'projects_objects':
$foreign_uids = $this->createQuery()
->statement('SELECT uid_foreign FROM tx_myext_item_object_mm')
->execute();
$constraints = [
$query->equals('isproject', 1),
$query->logicalNot($query->in('uid', $foreign_uids))
];
break;
case 'projects_only':
$constraints = $query->equals('isproject', 1);
break;
default:
$constraints = $query->equals('isproject', 0);
break;
}
$query->matching($query->logicalAnd($constraints));
return $query->execute();
}
the effort to build an array of all uid_foreign found in the tx_myext_item_object_mm table causes an error ...

Answer 1

This is, in my oppinion, a case for a custom query. The following should give you the objects not referenced to from within your mm-table:
$query = $this->createQuery();
$query->statement('
SELECT *
FROM tx_myext_domain_model_item
WHERE uid NOT IN(
SELECT foreign_uid FROM tx_myext_item_object_mm
)
');
$query->execute();