Get an array with DomainObjects in a single Extbase ControllerAction argument - typo3

Question

I'm creating an extbase extension to handle very simple product orders.
The model is:
Order --1:n--> OrderItem --1:1--> Product
To order a selection of products, the customer goes to checkout page and uses a Fluid based Order form. All selected products are available in the fluid template as {products}.
The OrderController->createAction processes new Orders by creating OrderItems from the given Products.
Writing the code I'd like to have would look like this:
class OrderController
{
public function create(Order $order, array $products)
{
foreach ($products as $product) {
$orderItem = new OrderItem()
->setProduct($product)
->setPrice($product->getPrice());
$order->addOrderItem($orderItem);
}
$this->orderRepository->add($order);
}
}
How to assign products to a Fluid form fields, in order to receive them as ControllerAction array argument?
How to trigger extbase to automagically provide an array of product objects to the ControllerAction?
I wonder if it is even possible to simplify the Controller createAction like shown below and assemble objects elsewhere:
public function create(Order $order) {
$this->orderRepository->add($order);
}

Answer 1

My suggestion for the fluid template would be:
// basic form with the order as main object
<f:form action="create" object="{order}">
// each order item with a product, using index to have no array with an empty index (Extbase does not like that)
<f:for each="{products}" key="index" as="product">
// Here you can set the product
<f:form.hidden prpoerty="orderItems.{index}.product" value="{product} />
</f:for>
</f:form>
This should be enough to use your single-line create action.
You can change the field type from select to whatever you want, but the __identity is mandatory to say Extbase which record it has to link.
When you want the orderItems to be new created, you need to remove the __identity field.