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Removing Items from a Collection


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Our brand-new user is the proud owner of two treasures with IDs 7 and 44. Let's update this user to see if we can make some changes to $dragonTreasures. Use the PUT endpoint, click "Try it out", and... let's see... the id we need is 14... so I'll enter that. I'll also remove every field except for dragonTreasures so we can focus.

We know that this currently has two dazzling treasures - /api/treasures/7 and /api/treasures/44. So if we send this request, in theory, that should do... nothing! And if we look down here... yeah: it made no changes at all.

Suppose we want to add a new DragonTreasure to this resource. To do that, we list the two that it already has, along with /api/treasures/8. I'm totally guessing that's a valid id. When we hit "Execute"... that works beautifully. The serializer system noticed that it already had these first two, so it didn't do anything with those. It just added the new one with id 8.

Removing an Item from a Collection

That's cool, but what I really want to talk about is removing a treasure. Let's say that our dragon left one of these treasures in their pants pocket and accidentally washed it in the laundry. I can't blame them. I lose my lip balm in there all the time. Since the treasure is soggy and useless now, we need to remove it from the list of treasures. No problem! We'll just mention the two our dragon still has and remove the other one. When we hit "Execute"... it explodes!

An exception occurred while executing a query: [...] Not null violation: 7. null value in column "owner_id"

What happened? Well, our app set the $owner property for the DragonTreasure we just removed to null... and is now trying to save it. But since we have it set to nullable: false, it's failing.

216 lines | src/Entity/DragonTreasure.php
// ... lines 1 - 55
class DragonTreasure
// ... lines 58 - 97
#[ORM\ManyToOne(inversedBy: 'dragonTreasures')]
#[ORM\JoinColumn(nullable: false)]
// ... lines 100 - 101
private ?User $owner = null;
// ... lines 103 - 214

But... let's take a step back and look at the whole picture. First, the serializer noticed that treasures 7 and 8 are already owned by the User... so it did nothing with those. But then it noticed that the treasure with id 44 - which was owned by this User - is missing!

Because of that, over on our User class, the serializer called removeDragonTreasure(). What's really important is that it takes that DragonTreasure and set the owner to null to break the relationship. Depending on your app, that might be exactly what you want. Maybe you allow dragonTreasures to have no owner... like... they're still undiscovered and waiting for a dragon to find them. If that's the case, you'll just want to make sure that your relationship allows null... and everything will save just fine.

But in our case, if a DragonTreasure no longer has an owner, we want to delete it completely. We can do that in User... way up on the dragonTreasures property. After cascade, add one more option here: orphanRemoval: true.

173 lines | src/Entity/User.php
// ... lines 1 - 22
class User implements UserInterface, PasswordAuthenticatedUserInterface
// ... lines 25 - 50
#[ORM\OneToMany(mappedBy: 'owner', targetEntity: DragonTreasure::class, cascade: ['persist'], orphanRemoval: true)]
// ... lines 52 - 53
private Collection $dragonTreasures;
// ... lines 55 - 171

This tells Doctrine that if any of these dragonTreasures become "orphaned" - meaning they no longer have any owner - they should be deleted.

Let's try it. When we hit "Execute" again... got it! It saves just fine.

Next: Let's circle back to filters and see how we can use them to search across related resources.