Re-adding addDroid(): Hide that Join Entity!
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This Chapter isn't quite ready...
Rest assured, the gnomes are hard at work
completing this video!
You might be asking yourself: "Hold up, do I really need to create a
StarshipDroid object every time I want to simply assign a droid to a starship?"
I think that's too much work. Could we get back to the good old days
when we could just call $ship->addDroid($droid)?
Yes! This won't work yet, but that's never stopped us before! Load up the fixtures. Ouch!
Undefined property:
App\Entity\Starship::$droids
Not exactly a surprise, as we're calling the long-dead droids property
in addDroid().
Remaking addDroid()
The first thing on our list is to
check if the Starship already has the droid in question. To
make this happen, switch the property to use the getDroids()
method. But wait, $this->getDroids()->add() isn't going to cut it.
Instead, we're going to roll up our sleeves and create the join entity
right here: $starshipDroid = new StarshipDroid()
$starshipDroid->setDroid($droid) and $starshipDroid->setStarship($this).
We've set the owning side of the relationship, but let's
sync up the other side too. We can do this by calling
$droid->starshipDroids->add($starshipDroid).
Give the fixtures another whirl:
symfony console doctrine:fixtures:load
Cascding the Persist
Ah ha, a new error. This one is pretty common in Doctrine, though not always easy to understand:
A new entity was found through the relationship
Starship#starshipDroidsthat was not configured to cascade persist for the entityStarshipDroid.
This is a very fancy way of saying we've created a new StarshipDroid
object and told Doctrine to persist its related Starship. But we
never told Doctrine to persist the StarshipDroid object itself.
Here's the rub: we don't have access to the entity manager. So we can't
just say $entityManager->persist($starshipDroid). Instead, we're going
to lean on something called cascade=["persist"], which I'll dive into that
right now.
