Doctrine 2 saving Entity with possible relations - php

Question

I am trying to save an Entity that may or may not already exist and may or may not have one or two relations (code below). My current method results in errors, I am pretty sure I could come up with some workarounds/hacks on my own, but I am interested in the proper, "official" way to do it.
What I am trying now:
$entity = new myEntity();
if ( !empty($id) )
{
$entity->setId($id);
}
$entity->setLocationId($relation_id); //may or may not be null, if not null it's always an already existing location entry in a different table, i.e. not a new
$entity = $entity_manager->merge($entity);
$entity_manager->flush();
Currently Doctrine complains about Location being a new Entity with no ID and the policy does not allow generating IDs automatically. Policy is indeed such, but I do not add Location entity at all, I use setLocationId() auto generated method which adds precisely existing Location's ID so I am a bit puzzled.
edit: I get the doctrine error when location id is not null but a real, existing (in db) location's id.
And the model:
Location:
type: entity
table: locationstable
id:
my-id-column:
type: string
fields:
some fields
oneToMany:
myEntities:
targetEntity: myEntity
mappedBy: location
cascade: ["persist", "merge"]

Answer 1

If you are going to use Doctrine 2's ORM then you really need to use it as designed. That means working with objects and not id's. If you are not comfortable with this approach then switch to some sort of active record implementation.
//For your case, start by seeing if there is an existing entity:
// This eliminates all the merge nonsense
$entity = $entityManager->getRepository('EntityClassName')->find($entityId);
if (!$entity)
{
$entity = new Entity();
/* Only do this is you are not autogenerating id's
* However, it does raise the question of how you know what the id should be if the entity
* if the entity does not yet exist?
*/
$entity->setId($id);
// Persist the new entity
$entityManager->persist($entity);
}
// Now get a reference to the location object which saves loading the entire location
// which optimizes things a tiny (probably unnoticeable) bit
$location = $entityManager->getReference('LocationClassName',$locationId);
$entity->setLocation($location);
// And flush changes
$entityManager->flush();
And again, if you feel this is too complex or uses too many queries then don't use Doctrine 2. You will be fighting it constantly. In practice, Doctrine 2 turns out to perform quite well. No real need to worry about micro-optimizations.

Answer 2

Try to find the location record and add to the entity:
$entity = new myEntity();
if ( !empty($id) )
{
$entity->setId($id);
}
//$entity->setLocationId($relation_id); //may or may not be null, if not null it's always an already existing
$location = $locationRepository->find($relation_id);
$entity->setLocation($location);
location entry in a different table, i.e. not a new
$entity = $entity_manager->merge($entity);
$entity_manager->flush();