[TYPO3-mvc] searching backward in model

[Johannes C. Schulz - EnzephaloN IT-Solutions]

Hello list!

I have a big problem, getting values of a parent-object.
I have a model called accreditation, that has (inline) childs called
persons.
Now I try to find the related accreditation of a person. I tried to
$this->accreditationRepository->findByUid($person->getAccreditation()); but
I got "Could not determine child object type". So I tried to write a
function returning just the accreditation-field, but I don't really know
how. The next try was to
$this->accreditationRepository->findByPersons($person); . But this returns
nothing.

A fourth idea was, simply to transfer the accreditation-object from one
action to another. But it seems, that inside a person-related partial, the
accreditation-object isn't available, or?

Has anyone an idea, how to get the parent object from a childobject?

Best regards

Johannes