Doctrine produces Integrity constraint violation 1451 - php

Question

As I cannot post the real code here, im using a substitute, that basically is the same, so please dont wonder if you find syntactic errors.
I have the following setup:
PHP 7.0,Symphony,Doctrine which is working with a MySQL database.
The classes are as following:
/*
* #ORM\Table(name="Postoffice")
* #ORM\Entity(repositoryClass="\AppBundle\Repsoitory\PostOfficeRepository")
*/
class Postoffice
{
/**
* Holds the Doctrine entity manager for database interaction
* #var EntityManager $em
*/
protected $em;
/**
* #var int
* #ORM\Column(name="id", type="integer")
* #ORM\Id
* #ORM\GeneratedValue(stragegy="AUTO")
*/
private $id;
/** #var ArrayCollection
* #ORM\ManyToMany(targetEntity="MailBox")
* #ORM\JoinTable(name="PostOfficeToMailBoxMapping",
* joinColumns={#ORM\JoinColumn(name="PostOfficeId",referencedColumnName="id")},
* inverseJoinColumns={#ORM\JoinColumn(name="MailBoxId",referencedColumnName="id",unique=true)})
*/
private $packets;
public function __construct(EntityManager $em)
{
$this->$packets = new ArrayCollection();
$this->em = $em;
}
}
/*
* #ORM\Table(name="PostStorage")
* #ORM\Entity(repositoryClass="\AppBundle\Repsoitory\PoststorageRepository")
*/
class Poststorage
{
/**
* Holds the Doctrine entity manager for database interaction
* #var EntityManager $em
*/
protected $em;
/**
* #var int
* #ORM\Column(name="id", type="integer")
* #ORM\Id
* #ORM\GeneratedValue(stragegy="AUTO")
*/
private $id;
/** #var ArrayCollection
* #ORM\ManyToMany(targetEntity="MailBox")
* #ORM\JoinTable(name="PostStorageToMailBoxesMapping",
* joinColumns={#ORM\JoinColumn(name="PoststorageId",referencedColumnName="id")},
* inverseJoinColumns={#ORM\JoinColumn(name="MailBoxId",referencedColumnName="id",unique=true)})
*/
private $MailBoxes;
public function __construct(EntityManager $em)
{
$this->MailBoxes = new ArrayCollection();
$this->em = $em;
}
public function delete()
{
//remove each box on its own
foreach ($this->Mailboxes as $iterMailBox)
$this->em->remove($iterMailBox);
$this->em->remove($this);
$this->em->flush();
}
}
/*
* #ORM\Table(name="MailBox")
* #ORM\Entity(repositoryClass="\AppBundle\Repsoitory\MailBoxRepository")
*/
class MailBox
{
/**
* #var int
* #ORM\Column(name="id", type="integer")
* #ORM\Id
* #ORM\GeneratedValue(stragegy="AUTO")
*/
private $id;
/** #var ArrayCollection
* #ORM\ManyToMany(targetEntity="Letter")
* #ORM\JoinTable(name="MailBoxToLetterMapping",
* joinColumns={#ORM\JoinColumn(name="MailBoxId",referencedColumnName="id")},
* inverseJoinColumns={#ORM\JoinColumn(name="LetterId",referencedColumnName="id",unique=true)})
*/
private $mailsInBox;
__construct()
{
$mailsInBox = new ArrayCollection();
}
}
class Letter
{
/**
* Holds the Doctrine entity manager for database interaction
* #var EntityManager $em
*/
protected $em;
/**
* #var int
* #ORM\Column(name="id", type="integer")
* #ORM\Id
* #ORM\GeneratedValue(stragegy="AUTO")
*/
private $id;
//lets assume this is a string
private $letterContent;
}
Now what im trying to model here is the following:
The Mailbox is somethinglike a container for a bunch of letters.
And a single mailbox can be at a certain point in its life only ba at one place at a time, and only at one. But the containers can be moved in between these two places. i.e. the Postoffice and the PostStorage.
The creation of these Mappings in the SQL database are not the Problem.
Letter N ------ 1 Mailbox (unidirectional with Join Tables)
MailBox N ------1 PostOffice or PostStorage (unidirectional with Join Tables)
The problem comes with the following feature. I want to be able to delete/merge/split individual containers and letters to and from containers and letters.
If im simply trying to delete a letter or Mailbox by using:
$em->remove($InstanceOfLetterOrMailBox);
$em->flush();
im getting the, in the title mentioned, "Integrity constraint violation".
As the Mailboxes can be at different places, i would really like to avoid to add refereces to the owner in the class, as it would bloat up the size of the class code very much, because i would like to add more places for the mailboxes to reside at in the future.
Ive spend the last few hours trying out different combinations of
Ondelete = CASCADE on different classes, but all I managed to do was either delete all classes from the db or not making a single delete, if im not getting the mentioned Error message back.
If you need more information let me know.
Thanks in advance.

Answer 1

I've found a solution to the problem. The problem was not that I was using the Cascade options incorrectly, but that i was trying to delete from an empty mailbox. In other words, I've been using a wrong index for my delete operation. The correct settings i am using now :
"cascade={"remove","persist"},orphanRemoval=true"
as a part of the many to many tag above the collection