Transforming data collected from form before persisting to entity - php

Question

I am a newbie at Symfony2 and just hacking my way through some existing codebase. I need help in understanding how to achieve the following outcome.
I have a PriceList entity that stores:
DollarCostPrice, PercentDiscount1, PercentDiscount2, PercentCommission
I want the user to enter following 4 values through a form:
SalePrice, DollarDiscount1Price, DollarDiscount2Price, PercentCommission
where,
SalePrice = (DollarCostPrice + (PercentCommission * DollarCostPrice))
DollarDiscount1Price = ((DollarCostPrice + (PercentCommission * DollarCostPrice)) * (100 - PercentDiscount1)/100)
DollarDiscount2Price = ((DollarCostPrice + (PercentCommission * DollarCostPrice)) * (1 - PercentDiscount2)/100)
But once user has entered the above values, I will compute DollarCostPrice, PercentDiscount1, PercentDiscount2, PercentCommission that need to be persisted in the entity.
I want to use a collection of above 4 fields in a form so that users can enter this information for multiple items at once.
I am still new with using forms, collections and data-transformers in Symfony2. I would appreciate if someone could help me determine the best way to do it.

Answer 1

I would do it this way. Note I'm making assumptions here, you haven't provided any information on what entities relate to PriceList for example.
Create a PriceListType form type, you would have 1 mapped field (PercentCommission) and 3 non-mapped fields (SalePrice, DollarDiscount1Price, DollarDiscount2Price)
To add a non-mapped field:
->add('SalePrice', null, array('mapped' => false))
I'm assuming that PriceList has a relation to some sort of SKU object or similar. You need to consider how you manage this relation.
Start with a basic form for your PriceList Type. I'd use something similar to this technique for adding new PriceList items.
On Save I would initially just do the entity calculations in the controller to get things up and running quickly E.g.
$yourForm->handleRequest($request);
if ($yourForm->isValid()) {
// loop through elements in your collection - note for non mapped fields
// you need to access them like so: $form->get("DollarDiscount1Price")->getData();
// calculate the data you wish to save to each PriceList entity, set and persist it
$entityManager->persist($priceListEntity);
// finish & finally flush
$entityManager->flush();
}
Then later I might move that functionality to a form event listener.
I don't see a need for a data transformer here myself as it'll add complexity. If you're planning to re-use this functionality in a number of forms maybe, but otherwise I don't think I'd worry about it.
People will tell you X is the ideal solution, but IMO start simple and refine as you go.