Call to a member function get...() on null - php

Question

Hello guys I need help.
I'm trying to build a forum for my website in symfony.
I have an entity Theme who regroup the entity Slug who regroup the entity Post.
When I navigate to the slug route to see the posts, I have the error "Call to a member function getSlug() on null".
But this function is called in another route.
Here is my different entity.
Theme
<?php
namespace App\Entity;
use App\Repository\ThemeRepository;
use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\Common\Collections\Collection;
use Doctrine\ORM\Mapping as ORM;
#[ORM\Entity(repositoryClass: ThemeRepository::class)]
class Theme
{
#[ORM\Id]
#[ORM\GeneratedValue]
#[ORM\Column(type: 'integer')]
private $id;
#[ORM\Column(type: 'string', length: 255)]
private $name;
#[ORM\Column(type: 'string', length: 255, nullable: true)]
private $imageName;
#[ORM\OneToMany(mappedBy: 'theme', targetEntity: Slug::class, orphanRemoval: true)]
private $slug;
public function __construct()
{
$this->slug = new ArrayCollection();
}
public function getId(): ?int
{
return $this->id;
}
public function getName(): ?string
{
return $this->name;
}
public function setName(string $name): self
{
$this->name = $name;
return $this;
}
public function getImageName(): ?string
{
return $this->imageName;
}
public function setImageName(?string $imageName): self
{
$this->imageName = $imageName;
return $this;
}
/**
* #return Collection<int, Slug>
*/
public function getSlug(): Collection
{
return $this->slug;
}
public function addSlug(Slug $slug): self
{
if (!$this->slug->contains($slug)) {
$this->slug[] = $slug;
$slug->setTheme($this);
}
return $this;
}
public function removeSlug(Slug $slug): self
{
if ($this->slug->removeElement($slug)) {
// set the owning side to null (unless already changed)
if ($slug->getTheme() === $this) {
$slug->setTheme(null);
}
}
return $this;
}
}
Slug
<?php
namespace App\Entity;
use App\Repository\SlugRepository;
use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\Common\Collections\Collection;
use Doctrine\ORM\Mapping as ORM;
#[ORM\Entity(repositoryClass: SlugRepository::class)]
class Slug
{
#[ORM\Id]
#[ORM\GeneratedValue]
#[ORM\Column(type: 'integer')]
private $id;
#[ORM\Column(type: 'string', length: 255)]
private $slugName;
#[ORM\OneToMany(mappedBy: 'slug', targetEntity: Post::class, orphanRemoval: true)]
private $posts;
#[ORM\ManyToOne(targetEntity: Theme::class, inversedBy: 'slug')]
#[ORM\JoinColumn(nullable: false)]
private $theme;
public function __construct()
{
$this->posts = new ArrayCollection();
}
public function getId(): ?int
{
return $this->id;
}
public function getSlugName(): ?string
{
return $this->slugName;
}
public function setSlugName(string $slugName): self
{
$this->slugName = $slugName;
return $this;
}
/**
* #return Collection<int, Post>
*/
public function getPosts(): Collection
{
return $this->posts;
}
public function addPost(Post $post): self
{
if (!$this->posts->contains($post)) {
$this->posts[] = $post;
$post->setSlug($this);
}
return $this;
}
public function removePost(Post $post): self
{
if ($this->posts->removeElement($post)) {
// set the owning side to null (unless already changed)
if ($post->getSlug() === $this) {
$post->setSlug(null);
}
}
return $this;
}
public function getTheme(): ?Theme
{
return $this->theme;
}
public function setTheme(?Theme $theme): self
{
$this->theme = $theme;
return $this;
}
}
Post
<?php
namespace App\Entity;
use App\Repository\PostRepository;
use Doctrine\ORM\Mapping as ORM;
#[ORM\Entity(repositoryClass: PostRepository::class)]
class Post
{
#[ORM\Id]
#[ORM\GeneratedValue]
#[ORM\Column(type: 'integer')]
private $id;
#[ORM\Column(type: 'text')]
private $content;
#[ORM\Column(type: 'datetime_immutable')]
private $createdAt;
#[ORM\Column(type: 'datetime_immutable', nullable: true)]
private $updatedAt;
#[ORM\ManyToOne(targetEntity: User::class, inversedBy: 'posts')]
#[ORM\JoinColumn(nullable: false)]
private $user;
#[ORM\ManyToOne(targetEntity: Slug::class, inversedBy: 'posts')]
#[ORM\JoinColumn(nullable: false)]
private $slug;
#[ORM\Column(type: 'string', length: 255, nullable: true)]
private $imageName;
public function getId(): ?int
{
return $this->id;
}
public function getTitle(): ?string
{
return $this->title;
}
public function setTitle(string $title): self
{
$this->title = $title;
return $this;
}
public function getContent(): ?string
{
return $this->content;
}
public function setContent(string $content): self
{
$this->content = $content;
return $this;
}
public function getCreatedAt(): ?\DateTimeImmutable
{
return $this->createdAt;
}
public function setCreatedAt(\DateTimeImmutable $createdAt): self
{
$this->createdAt = $createdAt;
return $this;
}
public function getUpdatedAt(): ?\DateTimeImmutable
{
return $this->updatedAt;
}
public function setUpdatedAt(?\DateTimeImmutable $updatedAt): self
{
$this->updatedAt = $updatedAt;
return $this;
}
public function getUser(): ?User
{
return $this->user;
}
public function setUser(?User $user): self
{
$this->user = $user;
return $this;
}
public function getSlug(): ?Slug
{
return $this->slug;
}
public function setSlug(?Slug $slug): self
{
$this->slug = $slug;
return $this;
}
public function getImageName(): ?string
{
return $this->imageName;
}
public function setImageName(?string $imageName): self
{
$this->imageName = $imageName;
return $this;
}
}
And here is my controller
<?php
namespace App\Controller;
use App\Repository\SlugRepository;
use App\Repository\ThemeRepository;
use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Routing\Annotation\Route;
class ForumController extends AbstractController
{
#[Route('/forum', name: 'forum')]
public function index(SlugRepository $slugRepository, ThemeRepository $themeRepository ): Response
{
$themes = $themeRepository->findAll();
return $this->render('forum/index.html.twig', [
'themes' => $themes,
]);
}
#[Route('/forum/{name}/{id}', name: 'theme')]
public function theme(string $name, $id, ThemeRepository $themeRepository ): Response
{
$themesId = $themeRepository->find($id);
$themes = $themeRepository->find($name);
$slugs = $themesId->getSlug();
$allThemes = $themeRepository->findAll();
return $this->render('forum/theme.html.twig', [
'themes' => $themesId,
'slugs' => $slugs,
'allThemes' => $allThemes,
]);
}
#[Route('/forum/{name}/{slugName}', name: 'slug')]
public function slug(string $name, string $slugName, $id,SlugRepository $slugRepository, ThemeRepository $themeRepository ): Response
{
$slugName = $slugRepository->find($slugName);
$slugsId = $slugRepository->find($id);
$themesId = $slugsId->getTheme()->getName($name);
$allThemes = $themeRepository->findAll();
return $this->render('forum/slug.html.twig', [
'themes' => $themesId,
'slugs' => $slugsId,
'allThemes' => $allThemes,
]);
}
}
I'm working on symfony 5.0.8
Thanks for your help.

Answer 1

In your method ForumController::theme the method $themeRepository->find() does not return a Theme object but null and $themes is unused.
$themesId = $themeRepository->find($id); // <- returns null
Solution: query by id and name explicitly.
$theme = $themeRepository->findOneBy([
'id' => $id,
'name' => $name
]);
if (!$theme) {
// log id and name, return a 404
}
$slug = $theme->getSlug();