TYPO3.Flow

Consider the following use case:

 1 <?php
 2 
 3 class SampleController extends \TYPO3\FLOW3\MVC\Controller\ActionController
 4     /**
 5      * 
 6      */
 7     public function initializeCreateAction() {
 8         $concreteClassName = $this->dummyFindOutConcreteProductProductClassName();
 9         $this->arguments['product']->setDataType($concreteClassName);
10     }
11 
12     /**
13      * @param \Acme\Northwind\Domain\Model\AbstractProduct $product
14      */
15     public function createAction(\Acme\Northwind\Domain\Model\AbstractProduct $product) {
16     }
17 }
18 ?>

Due to the fact that sub property's target types are settable, it makes sense (and is required for that use case) to allow setting the target type of an TYPO3\FLOW3\MVC\Controller\Argument, too.