[TYPO3-mvc] How to filter output when n:1 relation between objects?

[Roland]

>> You can call $productRepository->findByCountry($country_uid);
>
> or even cleaner, provide a country model instance:
> $productRepository->findByCountry($country);

does this mean, that it does not matter if you pass the id as an integer 
or the whole object?

thanks for the tipp!

question: is this relevant in my example where i have the get parameter, 
which can pe passed only?