Flashcard step 1 (ORM)

App\Entity\Flashcard.php

<?php

namespace App\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity
 */
class Flashcard
{
    /**
     * @ORM\Column(name="id", type="string", length=36)
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="CUSTOM")
     * @ORM\CustomIdGenerator(class="App\Util\Doctrine\UuidIdGenerator")
     */
    private $id;

    /**
     * @ORM\Column(type="string", length=255)
     */
    public $question;

    /**
     * @ORM\Column(type="string", length=255)
     */
    public $answer;

    /**
     * @ORM\ManyToOne(targetEntity="Lesson", inversedBy="flashcards")
     */
    public $lesson;

    public function __construct($id = null)
    {
        $this->id = $id;
    }
  
    public function getId(): ?string
    {
        return $this->id;
    }
}

App\Entity\Lesson.php

<?php

namespace App\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity
 */
class Lesson
{
    /**
     * @ORM\Column(name="id", type="string", length=36)
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="CUSTOM")
     * @ORM\CustomIdGenerator(class="App\Util\Doctrine\UuidIdGenerator")
     */
    private $id;

    /**
     * @ORM\Column(type="string", length=255)
     */
    public $name;

    /**
     * @ORM\OneToMany(targetEntity="Flashcard", mappedBy="lesson", cascade={"persist", "remove"})
     */
    public $flashcards;

    /**
     * @ORM\ManyToOne(targetEntity="Subject", inversedBy="lessons")
     */
    public $subject;

    public function __construct($id = null)
    {
        $this->id = $id;
    }

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

App\Entity\Subject.php

<?php

namespace App\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity
 */
class Subject
{
    /**
     * @ORM\Column(name="id", type="string", length=36)
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="CUSTOM")
     * @ORM\CustomIdGenerator(class="App\Util\Doctrine\UuidIdGenerator")
     */
    private $id;

    /**
     * @ORM\Column(type="string", length=255)
     */
    public $name;

    /**
     * @ORM\OneToMany(targetEntity="Lesson", mappedBy="subject", cascade={"persist", "remove"})
     */
    public $lessons;

    /**
     * @ORM\ManyToOne(targetEntity="User")
     */
    public $user;

    public function __construct($id = null)
    {
        $this->id = $id;
    }

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

App\Entity\User.php

<?php

namespace App\Entity;

use Doctrine\ORM\Mapping as ORM;
use Symfony\Component\Security\Core\User\UserInterface;

/**
 * @ORM\Entity()
 * @ORM\Table(name="`user`")
 * @UniqueEntity("email")
 */
class User implements UserInterface
{
    /**
     * @ORM\Column(type="string", length=36)
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="CUSTOM")
     * @ORM\CustomIdGenerator(class="App\Util\Doctrine\UuidIdGenerator")
     */
    private $id;

    /**
     * @ORM\Column(type="string", length=255)
     */
    public $name;

    /**
     * @ORM\Column(type="string", length=255, unique=true)
     */
    public $email;

    /**
     * @ORM\Column(type="string", length=64)
     */
    public $password;

    /**
     * @ORM\Column(type="json_array")
     */
    public $roles;

    public $plainPassword;

    public function __construct($id = null)
    {
        $this->id = $id;
    }

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

    public function getRoles()
    {
        return $this->roles;
    }

    public function getPassword()
    {
        return $this->password;
    }
  
    public function getSalt()
    {
        return null;
    }
  
    public function getUsername()
    {
        return $this->name;
    }

    public function eraseCredentials()
    {
        $this->plainPassword = null;
    }
}

App\Util\Doctrine\UuidIdGenerator.php

<?php

namespace App\Util\Doctrine;

use Doctrine\ORM\EntityManager;
use Doctrine\ORM\Id\AbstractIdGenerator;

class UuidIdGenerator extends AbstractIdGenerator
{
    public function generate(EntityManager $em, $entity)
    {
        if ($entity->getId() !== null) {
            return $entity->getId();
        }

        return \Ramsey\Uuid\Uuid::uuid4();
    }
}