Symfony2: How to create entity form with creation of multiple subentities? - forms

Question

This is propably a simple task to solve in Symfony2 but I am really stuck here:
I am building a very simple shop. There are three entities: Products, Customers, and Orders. The last one contains three columns: customer_id, product_id, and quantity. The shop simply consists of a page listing all the products with a select field for each to chose the quantity, followed by a form to enter your customer data.
I have no problem creating the form for the customer data nor listing the products itself (without the select fields).
But how do I create a form including the select fields of the products, which then should become order entities?
I played around with form collections and I do understand all the given examples with adding tags to an entity etc. But I can't get the hang of how to adjust it to my situation.
What I have in mind goes something like this:
// Create new customer
$customer = new Customer();
// At this point, create form and validate it.
// Having trouble here, need a hint to get it right.
...
// If form is ok, loop thru all the products.
// Since I do not know yet how to define the form,
// I don't know yet what to loop over, too.
foreach( ..... ){
if($quantity > 0){
$order = new Order();
$order->setQuantity($quantity);
$order->setProduct($product);
$customer->addOrder($order);
}
}
// then persist $customer, cascading its orders.
...
I have been spending hours on this. Any help is greatly appreciated. Thanks!
Update:
Eventually I got it working. I created an OrderFactory and a OrderFormType and had to change around the whole setting a bit. The AcmePizzaBundle which is mentioned in the responses below was actually a great help to get the missing parts right.

Answer 1

Take a look at an example: AcmePizzaBundle.
It has 4 entities you need: Pizza, Order, OrderItem, Customer.