Doctrine entities reference each other's primary key - php

Question

I have an Account entity which contains a collection of Group entities. In addition, each Account must have a default Group. How can one persist the entities? When attempting to do so, $manager->flush(); complains with a Not null violation for the entity that was persisted first.
Account:
namespace App\Entity;
use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\Common\Collections\Collection;
use Symfony\Bridge\Doctrine\IdGenerator\UuidV4Generator;
use Doctrine\ORM\Mapping as ORM;
/**
* #ORM\Entity()
*/
class Account
{
/**
* #ORM\Id
* #ORM\Column(type="uuid", unique=true)
* #ORM\GeneratedValue(strategy="CUSTOM")
* #ORM\CustomIdGenerator(class=UuidV4Generator::class)
*/
private $id;
/**
* #ORM\OneToOne(targetEntity=Group::class, cascade={"persist", "remove"})
* #ORM\JoinColumn(nullable=false, unique=true)
*/
private $defaultGroup;
/**
* #ORM\OneToMany(targetEntity=Group::class, mappedBy="account")
*/
private $groups;
public function __construct()
{
$this->groups = new ArrayCollection();
$this->defaultGroup = new Group();
}
// Typical getters and setters
}
Group:
namespace App\Entity;
use Doctrine\ORM\Mapping as ORM;
/**
* #ORM\Entity()
*/
class Group
{
/**
* #ORM\Id
* #ORM\GeneratedValue
* #ORM\Column(type="integer")
*/
private $id;
/**
* #ORM\ManyToOne(targetEntity=Account::class, inversedBy="groups")
* #ORM\JoinColumn(nullable=false, onDelete="CASCADE")
*/
private $account;
// Typical getters and setters
}

Answer 1

Your approach is not possible because Group::$account is already mapped to the one-to-many Account::$groups property. Doctrine does not know what to do when you persist a Group via Account::$defaultGroup, as this is not the property Group::$account is inversing.
You will have to enforce this Account default group invariant yourself programmatically. There's multiple approaches to this, but I suggest using the existing Account::$groups mapping in combination with the Symfony Collection validation constraint. Validating that an Account should have at least 1 Group assigned to it, which will be the default one.
Here's an example:
Because the entity name Group was giving me syntax problems in the SQL dialect I was using I renamed it to Team.
The Account implementation:
<?php declare(strict_types = 1);
namespace App\Entity;
use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\Common\Collections\Collection;
use Doctrine\ORM\Mapping as ORM;
use Symfony\Component\Validator\Constraints as Assert;
/**
* #ORM\Entity
*/
class Account
{
/**
* #ORM\Id
* #ORM\GeneratedValue
* #ORM\Column(type="integer")
*/
private ?int $id = null;
/**
* #ORM\OneToMany(
* targetEntity="App\Entity\Team",
* mappedBy="account",
* cascade={"persist", "remove"},
* )
* #Assert\Count(
* min=1
* )
*/
private Collection $teams;
public function __construct()
{
$this->teams = new ArrayCollection();
$this->addTeam(new Team());
}
public function getId(): ?int
{
return $this->id;
}
public function getDefaultTeam(): ?Team
{
$team = $this->teams->first();
return $team instanceof Team ? $team : null;
}
public function getTeams(): Collection
{
return $this->teams;
}
public function setTeams(array $teams): void
{
$this->teams->clear();
foreach ($teams as $team) {
if ($team instanceof Team) {
$this->addTeam($team);
}
}
}
public function addTeam(Team $team): void
{
if (false === $this->teams->contains($team)) {
$this->teams->add($team);
$team->setAccount($this);
}
}
public function removeTeam(Team $team): void
{
if (true === $this->teams->contains($team)) {
$this->teams->removeElement($team);
}
}
}
The Team implementation:
<?php declare(strict_types = 1);
namespace App\Entity;
use Doctrine\ORM\Mapping as ORM;
/**
* #ORM\Entity
*/
class Team
{
/**
* #ORM\Id
* #ORM\GeneratedValue
* #ORM\Column(type="integer")
*/
private ?int $id = null;
/**
* #ORM\ManyToOne(
* targetEntity="App\Entity\Account",
* inversedBy="teams",
* )
* #ORM\JoinColumn(
* name="account_id",
* referencedColumnName="id",
* nullable=false
* )
*/
private ?Account $account = null;
public function getId(): ?int
{
return $this->id;
}
public function getAccount(): ?Account
{
return $this->account;
}
public function setAccount(Account $account): void
{
$this->account = $account;
}
}