Symfony Impossible to access an attribute ("nameArticle") on a null variable

Question

I created a blog and there is a comment system. I have a little problem to post my comments. When comments exist the articles are correctly displayed with their comments, but the problem when an article does not have a comment, it shows me an error like this

Impossible to access an attribute ("nameArticle") on a null variable.

I tried to add a if but it does not work it does not show me the article!

my controller:

/**
 * @Route("/{slug}")
 * @param string $slug
 * @param Request $request
 * @return Response
 * @throws \Exception
 */
 public function detail(Request $request, string $slug): Response {

     $article = $this->getDoctrine()
         ->getRepository(Articles::class)
         ->findOneWithCategorySlug($slug);

     $info = $this->getDoctrine()
         ->getRepository(InfoMore::class)
         ->findByInfo(2);

     // $comments = $this->getDoctrine()->getRepository(Comments::class)->findAll();

     $comment = new Comments();
     $form = $this->createForm(CommentsType::class, $comment);
     $form->handleRequest($request);

     if($form->isSubmitted() && $form->isValid()) {

         $comments = $form->getData();
         $manager = $this->getDoctrine()->getManager();
         $user = $this->getUser();
         $comments->setUserComments($user);
         $comments->setArticleComments($article);
         $manager->persist($comments);
         $manager->flush();
         $this->addFlash('notice', 'Le commentaire a bien été ajouté ');
         return $this->redirectToRoute('app_home_detail', [
             'slug' => $slug
         ]);
     }

     return $this->render('front/detail_article.html.twig', [
         'title' => $article,
         'article' => $article,
         'info' => $info,
         'description' => '',
         'keywords' => '',
         'addComments' => $form->createView()
    ]);
}

my view:

{% extends 'base.html.twig' %}

{% set active = '' %}
{% set active2 = '' %}
{% set active3 = '' %}
{% set active4 = '' %}
{% set active5 = '' %}
{% set active6 = '' %}

{% if title %}
{% set title = article.nameArticle %}
{% else %}
    {% set title = 'Erreur article non trouver !' %}
{% endif %}

{% block body %}

        
            
                
                    

                      {{ article.nameArticle }}

                    
                
            
        


    


    

        
            Article publié le : {{ article.createdAt | date('d/m/Y à H:i') }} dans {{ article.category }}
        


            {{ article.introduction | raw }}


        
            
               
            
        
        
        
            
            ×
            
            
            
            
        

            {{ article.articleContent |raw }}

    

   

{% for comment in article.comments %}
    {{ comment.commentsContent }} de la part {{ comment.userComments }}
{% endfor %}


   

 {% if is_granted("IS_AUTHENTICATED_REMEMBERED") %}

     {% for message in app.flashes('notice') %}
         
         

             {{ message }}
             
         
         
     {% endfor %}

   {{ form_start(addComments) }}
        
            
                    {{ form_widget(addComments) }}
                    {{ form_errors(addComments) }}
                
            
        
   {{ form_end(addComments) }}
        {% endif %}
    

    

{% endblock %}

and my repository:

 /**
  * @param string $slug
  * @return Articles|null
  * @throws \Exception
  */
  public function findOneWithCategorySlug(string $slug): ?Articles {

      $query = $this->createQueryBuilder('a')
          ->join('a.category', 'c')
          ->addSelect('c')
          ->where('a.slug = :slug')
          ->setParameter(':slug', $slug)
          ->innerJoin('a.comments', 'com')
          ->getQuery()
      ;

      try {
          return $query->getOneOrNullResult();
      } catch (\Exception $e) {
          throw new \Exception('Problème dans ArticlesRepository::findOneWithCategory' . $e->getMessage() . var_dump($e));
      }

  }

fgamess · Accepted Answer

That's normal, in your query you use innerJoin.

The INNER JOIN keyword selects records that have matching values in both tables.

So your query will only select records that have matching values in both Articles and Comments tables. If there are no comments, the record with the Article found won't be selected.

If you want to get rid of

Impossible to access an attribute ("nameArticle") on a null variable.

Just fix your twig by using not null and you can add defined to enforce your verification:

{% if article is defined and article is not null %}
    {% set title = article.nameArticle %}
{% else %}
    {% set title = 'Erreur article non trouver !' %}
{% endif %}

If you want to display Articles even if they don't have comments use leftJoin instead of innerJoin:

/**
 * @param string $slug
 * @return Articles|null
 * @throws \Exception
 */
public function findOneWithCategorySlug(string $slug): ?Articles {

    $query = $this->createQueryBuilder('a')
        ->join('a.category', 'c')
        ->addSelect('c')
        ->where('a.slug = :slug')
        ->setParameter(':slug', $slug)
        ->leftJoin('a.comments', 'com')
        ->getQuery()
    ;

    try {
        return $query->getOneOrNullResult();
    } catch (\Exception $e) {
        throw new \Exception('Problème dans ArticlesRepository::findOneWithCategory' . $e->getMessage() . var_dump($e));
    }

}

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