How should a `FormType` be structured in order to include an `EntityType` field which doesn't exist in the `FormType` entity?

Question

Taking the below as an example, OrderType is based on the entity Order. The form that is required needs to contain the following two EntityType dropdowns within it: <

Answer 1

As you say, adding a Category property to the Order entity just for forms is less than ideal. What I would do is make a OrderCategoryType and pass in Order and Category as an array.

// Controller
$order = new Order();
$category = new Category();  // Or create from $order->getProduct()
$data = ['order' => $order, 'category' => $category);

$form = $this->createFormBuilder($data)
  ->add('order',new OrderType(),
  ->add('category',new CategoryType()
);

You will have to do some messing around to keep everything in sync but it should work just fine.