როგორ განვახორციელოთ 'has many through' ურთიერთობა Doctrine-ში?

V Doctrine2, odnosot "has many through" se realizira chrez yavno syzdavane na mezhdina sushtnost (join entity), koyato svurzva dve drugi sushtnosti s otnosheniya Many-to-One.

1. Syzdavat se tri klasa sushtnosti: Iztochnata, Tselnata i Mezhdina (JoinEntity).

2. Mezhdinata sushtnost (naprimer, UserGroup za "User has many Group through UserGroup") sadrzha dve polyta, koito sa otnosheniya Many-to-One kŭm Iztochnata (User) i Tselnata (Group) sushtnosti.

3. Iztochnata i Tselnata sushtnosti imat otnoshenie One-to-Many kŭm Mezhdinata sushtnost.

4. Za udobstvo pri dostŭpa do Tselnite sushtnosti chrez Iztochnata (naprimer, da poluchite vsichki Group za User), mozhe da dobavite metoda v Iztochnata sushtnost, koyato shte filtirira Mezhdinite sushtnosti.

Primerna struktura:

// User.php
<?php

use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\Common\Collections\Collection;
use Doctrine\ORM\Mapping as ORM;

#[ORM\Entity]
class User
{
    #[ORM\Id]
    #[ORM\GeneratedValue]
    #[ORM\Column]
    private ?int $id = null;

    #[ORM\OneToMany(targetEntity: UserGroup::class, mappedBy: 'user')]
    private Collection $userGroups; // Otnoshenie kŭm mezhdinata sushtnost

    public function __construct()
    {
        $this->userGroups = new ArrayCollection();
    }

    public function getId(): ?int
    {
        return $this->id;
    }

    /**
     * Poluchavane na grupite na potrebitelq chrez mezhdinata sushtnost.
     * Tova e ekvivalent na "has many through".
     * Zamechka: Moje da iskate da izpolzvate tozi kolektsiya efektivno v zavisimost ot nuzhdate si.
     */
    public function getGroups(): Collection
    {
        return $this->userGroups->map(fn(UserGroup $userGroup) => $userGroup->getGroup());
    }

    public function getUserGroups(): Collection
    {
        return $this->userGroups;
    }

    public function addUserGroup(UserGroup $userGroup): static
    {
        if (!$this->userGroups->contains($userGroup)) {
            $this->userGroups->add($userGroup);
            $userGroup->setUser($this);
        }

        return $this;
    }

    public function removeUserGroup(UserGroup $userGroup): static
    {
        if ($this->userGroups->removeElement($userGroup)) {
            // postavi stranata na null (ako ne e promenena veche)
            if ($userGroup->getUser() === $this) {
                $userGroup->setUser(null);
            }
        }

        return $this;
    }
}

// Group.php
<?php

use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\Common\Collections\Collection;
use Doctrine\ORM\Mapping as ORM;

#[ORM\Entity]
class Group
{
    #[ORM\Id]
    #[ORM\GeneratedValue]
    #[ORM\Column]
    private ?int $id = null;

    #[ORM\OneToMany(targetEntity: UserGroup::class, mappedBy: 'group')]
    private Collection $userGroups; // Vzťah k prepojovacej entite

    public function __construct()
    {
        $this->userGroups = new ArrayCollection();
    }

    public function getId(): ?int
    {
        return $this->id;
    }

    public function getUserGroups(): Collection
    {
        return $this->userGroups;
    }

    public function addUserGroup(UserGroup $userGroup): static
    {
        if (!$this->userGroups->contains($userGroup)) {
            $this->userGroups->add($userGroup);
            $userGroup->setGroup($this);
        }

        return $this;
    }

    public function removeUserGroup(UserGroup $userGroup): static
    {
        if ($this->userGroups->removeElement($userGroup)) {
            // postavi stranata na null (ako ne e promenena veche)
            if ($userGroup->getGroup() === $this) {
                $userGroup->setGroup(null);
            }
        }

        return $this;
    }
}

// UserGroup.php
<?php

use Doctrine\ORM\Mapping as ORM;

#[ORM\Entity]
#[ORM\Table(name: 'user_user_group')] // Primer za ime na tablicata
class UserGroup
{
    #[ORM\Id]
    #[ORM\GeneratedValue]
    #[ORM\Column]
    private ?int $id = null;

    #[ORM\ManyToOne(targetEntity: User::class, inversedBy: 'userGroups')]
    #[ORM\JoinColumn(nullable: false)]
    private ?User $user = null; // Many-to-One kŭm User

    #[ORM\ManyToOne(targetEntity: Group::class, inversedBy: 'userGroups')]
    #[ORM\JoinColumn(nullable: false)]
    private ?Group $group = null; // Many-to-One kŭm Group

    public function getId(): ?int
    {
        return $this->id;
    }

    public function getUser(): ?User
    {
        return $this->user;
    }

    public function setUser(?User $user): static
    {
        $this->user = $user;

        return $this;
    }

    public function getGroup(): ?Group
    {
        return $this->group;
    }

    public function setGroup(?Group $group): static
    {
        $this->group = $group;

        return $this;
    }
}

Tози подход, макар и да изисква създаването на допълнителна същност, дава пълен контрол върху данните за връзките и позволява лесно добавяне на допълнителни полета в междинната таблица (например, дата на присъединяване на потребителя към група).