Symfony delete ManyToMany related object when one part is empty? - php

Question

I'm trying to delete unused tags. Although the relationship between Post and Tag has been deleted, the post-linked tag is not deleted.
"orphanRemoval" does not work because it has deleted all. cascade "remove" does not delete.
Post Entity:
class Post implements \JsonSerializable
{
/**
* #ORM\ManyToMany(targetEntity="App\Entity\Cms\PostTag", inversedBy="posts", cascade={"persist", "remove"})
* #ORM\JoinTable(name="post_tag_taxonomy")
* #Assert\Count(max="5")
*/
private $tags;
}
Tag Entity:
class PostTag {
/**
* #ORM\ManyToMany(targetEntity="App\Entity\Cms\Post", mappedBy="tags")
*/
private $posts;
}
Here's a similar example, but for Java. How to delete an ManyToMany related object when one part is empty?

Answer 1

I suggest you use preUpdate event from Doctrine life cycle callbacks. On the event of update a Post, you tell doctrine to check if there's a Tag change (in this case it's to NULL), if yes then query the Tag check if any posts still use it.
In short, you need to :
Add #ORM\HasLifecycleCallbacks before your class to enable life cycles.
Add preUpdate function in Post class :
/**
* #ORM\PreUpdate
* #param PreUpdateEventArgs $event
*/
public function clearChangeSet(PreUpdateEventArgs $event)
{
if ($event->hasChangedField('field_you_want_to_check')
) {
$em = $event->getEntityManager();
// Now use the entityManager to query the tag and check.
}
}
By doing this doctrine will do the check for you, in the logic code you just need to perform the unlinking, no need to care about delete tags there.
Update : as pointed out, for associations in entity you cannot get the changes by $event->hasChangedField, use the method in Symfony 3 / Doctrine - Get changes to associations in entity change set

Answer 2

Solution:
/**
* #ORM\PostUpdate()
*/
public function postUpdate(LifecycleEventArgs $args)
{
/** #var PersistentCollection $tags */
$tags = $args->getEntity()->getTags();
if ($tags->isDirty() && ($deleted = $tags->getDeleteDiff())) {
$em = $args->getEntityManager();
foreach ($deleted as $tag) {
if ($tag->getPosts()->count() === 1) {
$em->remove($tag);
$em->flush($tag);
}
}
}
}