Empty and/or Filter ObjectStorage objects - typo3

Question

I have an object appointment with a property expertises of type \TYPO3\CMS\Extbase\Persistence\ObjectStorage<\Vendor\Extname\Domain\Model\Expertise>.
Additionally one important property of Expertise is the bool checked.
What I want to do in my AppointmentController is:
In the first action: Empty the appointment's property expertises (not set it to NULL, I just want an empty ObjectStorage that I can add something to later)
In the second action: Fill appointment with expertises (from a different object) whose property checked equals true
To start out with the emptying I looked at the answer from here but it didn't work for me.
This is what I tried:
$appExp = $appointment->getExpertises();
foreach ($appExp as $exp) {
$appExp->detach($exp);
}
\TYPO3\CMS\Extbase\Utility\DebuggerUtility::var_dump($appointment);
But it shows that all expertises are still in appointment.
In the second action I do this:
foreach ($expertises as $expertise) {
if ($expertise->getChecked()) {
$appointment->addExpertise($expertise);
}
}
It works, but I wonder if there's an easier "filter" function that can automatically filter the checked value and return an ObjectStorage object. Because this way I could just use setExpertises() and the old ones would get overwritten which would make the first step unnecessary.
So does someone have an idea for the emptying and filtering of ObjectStorage objects?
I looked a bit into the ObjectStorage Class reference but there's no obvious function that empties it (removeAll ist just for objects contained in another storage from the current storage) and no filter function either.

Answer 1

There is an easy way to remove all objects from the object storage:
$appointment->getExpertises()->removeAll($appointment->getExpertises());
As for filtering: as you already noticed, you have to do it yourself. I would implement such functions like getActiveExpertises in the Model, because it fits there much better than in a controller.

Answer 2

The setters in ExtbaseObjects that refer to ObjectStorages have an optional parameter that defaults to null. Just call the setter without a parameter. You don't have to waste performance by instanciating an empty StorageObject.
$appointment->setExpertises();