====== Formulaire complet avec entité, ajout et édition ======

===== Formulaire =====

<code php ArticleType.php>
use App\Entity\Article;
use App\Entity\Categorie;
use Symfony\Bridge\Doctrine\Form\Type\EntityType;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;

class ArticleType extends AbstractType {

    public function buildForm(FormBuilderInterface $builder, array $options) {
        $builder
            ->add('titre')
            ->add('contenu')
            ->add('image')
            ->add('categorie', EntityType::class, [
                'class'        => Categorie::class,
                'choice_label' => 'titre',
                'required'     => false               // si on veut pouvoir ne rien choisir
            ])
        ;
    }
    
    public function configureOptions(OptionsResolver $resolver) {
        $resolver->setDefaults([
            'data_class' => Article::class,
        ]);
    }
}
</code>

===== Contrôleur =====

<code php ArticlesController.php>
use App\Entity\Article;
use App\Form\ArticleType;
use Doctrine\ORM\EntityManagerInterface;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\Routing\Annotation\Route;

...

/**
 * @Route("/articles/create", name="creer_article")
 * @Route("/articles/{id}/edit", name="editer_article")
 */
public function edit(
    Article $article = null,
    Request $request,
    EntityManagerInterface $manager
) {

    // Si l'article est null, on est dans l'ajout d'un nouvel article,
    // sinon on est dans l'édition d'un article existant.
    if(!$article)
        $article = new Article();

    $form = $this->createForm(ArticleType::class, $article);
    $form->handleRequest($request);

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

        // Si c'est un nouvel article, initialiser sa date de création
        if(!$article->getId()) {
            $article->setCreatedAt(new \DateTime());
        }

        $manager->persist($article);
        $manager->flush();

        return $this->redirectToRoute('voir_article', [
            'id' => $article->getId()
        ]);
    }

    return $this->render('articles/edit.html.twig', [
        'formArticle' => $form->createView(),
        'editMode'    => $article->getId() !== null,
    ]);
}
</code>

===== edit.html.twig =====

<code twig>
{% extends 'base.html.twig' %}
{% form_theme formArticle 'bootstrap_4_layout.html.twig' %}

{% block body%}

{{ form_start(formArticle) }}

{{ form_row(formArticle.title, {
   'label': 'Titre',
   'attr': {'placeholder': "Titre de l'article"},
}) }}

{{ form_row(formArticle.content, {
   'label': 'Contenu',
   'attr': {'placeholder': "Contenu de l'article"},
}) }}

{{ form_row(formArticle.image, {
   'label': 'Image',
   'attr': {'placeholder': "URL de l'image"}
}) }}

<button type="submit" class="btn btn-primary">
{% if editMode %}
   Enregistrer les modifications
{% else %}
   Ajouter l'article
{% endif %}
</button>

{{ form_end(formArticle) }}

{% endblock %}
</code>