What is the better solution to get the Entity I want in a biderectional OneToMany relation? - symfony

Question

I have one entity Article and an other entity Image with a bidrectional relation OneToMany and ManyToOne :
class Article
{
/**
* #ORM\OneToMany(targetEntity="AppBundle\Entity\Image", mappedBy="article")
*/
private $images;
}
class Image
{
/**
* #ORM\ManyToOne(targetEntity="AppBundle\Entity\Article", inversedBy="images")
* #ORM\JoinColumn(nullable=true)
*/
private $article;
}
In my controller I use #paramconverter to get the article I want :
/**
* #Route("/blog/{slug}", name="article")
* #ParamConverter("article", class="AppBundle:Article")
*/
public function articleAction(Article $article)
{
return $this->render('default/article.html.twig', array(
'article' => $article,
));
}
Now my problem is that I want to identify the ONLY image with the attributes "main = true" in all the "article.images" I have.
What is the best solution?
In my wiew I can do somehting like this but it's not the best I think :
{% for image in article.images %}
{% if image.main %}
<img src="{{ asset( image.src ) }}" alt="{{ image.alt }}" title="{{ image.title }}">
{% endif %}
{% endfor %}
I'd like to use something like :
{{ article.mainImg }}
How can I achieve this please? And is this the best solution?

Answer 1

Doctrine provides a collection filter mechanism you could use to get the "main image":
public function articleAction(Article $article)
{
$criteria = Criteria::create()
->where(Criteria::expr()->eq("main", true))
->setMaxResults(1);
$mainImg = $article->getImages()->matching($criteria)->first();
return $this->render('default/article.html.twig', array(
'article' => $article,
'mainImg' => $mainImg
));
}
More information on filtering doctrine collections: Filtering collections
I did not test the code myself, but it should convey the idea of how it can be done.