[TYPO3-mvc] getting the arguments of the form?

[Stig Nørgaard Færch]

I could have input form with the name:
tx_myext_user_myextadmin[person][streetName]

then I could get the person array with:
$this->request->getArgument('person');

But is possible to check directly on above input field?
It doesn't seem like getArgument does the job here - but are there other 
methods to use?

/Stig