Doctrine2应自动合并关联的实体

Question

I am building an order process, in which an Order object is built through many steps. After each step I put the partly finished Order object into the session , and in the final step I save it into the database.

During the steps I load other, (already existing) associated objects into my Order object(eg. DiscountCoupon ). The problem is that when I save my Order to the session and then load it in the next step, all associated entities will be detached. So when I want to save it to the database, the EntityManager throws an exception, which asks for setting a cascade=persist on the relationship.

Of course, I dont need to persist those objects(they are already in the database). The obvious solution could be to change those associated objects to merged ones(using EntityManager#merge method), however, I have a rather complicated object structure with multiple levels of embedded entities, so doing the above process would be rather inconvinient.

Cannot Doctrine automatically do this task for me? So instead of 'complaining' about my detached entities, it could automatically merge them.

Answer 1

As far as I can tell, you'd be creating some serious magic if you tried to make it entirely automatic.

Your best bet is probably to implement a function with a signature like: mergeOrderEntities($Order, $EntityManager) which knows how to talk the Order structure and invoke EntityManager::merge() on all detached associated entities.

As to why doctrine doesn't do this automatically, I'm not sure. I suspect there are use cases where auto-merging of entities could be dangerous, or at least undesirable.