Create form with two choices fileds - symfony

Question

I want create two choces field like that, because if i generate form i have problem with __toString() method, because i need to fields passed to the function.
/**
* #Route("/transport", name="transportAction")
* #Template("CoreBundle:Goods:transport.html.twig")
*/
public function transportAction()
{
$storageItems = new StorageItems();
$form = $this->createFormBuilder($storageItems)
->add('storageitems_to_deliveries', 'entity', [
'class' => 'ModelBundle:Deliveries',
'choices' => $storageItems->getStorageitemsToDeliveries()
])
->add('storageitems_to_strorage', 'entity', [
'class' => 'ModelBundle:Storages',
'choices' => $this->getDoctrine()->getRepository('ModelBundle:Storages')->findAll(),
//'property'=> 'secondStorage'
])
->getForm();
return array(
'form' => $form->createView()
);
}
In result i have error
Warning: Illegal offset type
What i do wrong? How fixed it?
P.S
class Deliveries
{
/**
* #var integer
*
* #ORM\Column(name="id", type="integer")
* #ORM\Id
* #ORM\GeneratedValue(strategy="AUTO")
*/
private $id;
/**
* #ORM\ManyToOne(targetEntity="Items", inversedBy="items_to_deliveries")
* #ORM\JoinColumn(name="items_to_deliveries_id", referencedColumnName="id", nullable=false)
*/
private $deliveries_to_items;
/**
* #ORM\ManyToOne(targetEntity="Workers", inversedBy="workers_to_deliveries")
* #ORM\JoinColumn(name="workers_to_deliveries_id", referencedColumnName="id", nullable=false)
*/
private $deliveries_to_workers;
/**
* #var ArrayCollection
* #ORM\OneToMany(targetEntity="StorageItems", mappedBy="storageitems_to_deliveries", cascade={"remove"})
*/
private $deliveries_to_storageitems;
public function __construct()
{
$this->deliveries_to_storageitems = new ArrayCollection();
}
public function __toString()
{
return $this->deliveries_to_workers;
}

Answer 1

I see three issues here (2 major, 1 minor):
$this->getDoctrine()->getRepository('ModelBundle:Deliveries')
This will return an array of Deliveries objects. Symfony2 has no way of determining the textual representation needed for label, unless you implement __toString() (major)
In addition, array will be numerically indexed. The values for form elements will be 0, 1, etc... This can cause some inexplicable behaviors and headaches along the way. You should consider returning array which uses object ID as it's key. (minor issue)
'data' => ''
Hit this wall a few times. data attribute will override everything and anything, be it a default entity member value or the value that came from Request. Be careful when using it ;) (major)
Hope this helps...