How to Embed Controllers in a Template

Including template fragments is useful to reuse the same content on several pages. However, this technique is not the best solution in some cases.

Consider a website that displays on its sidebar the most recently published articles. This list of articles is dynamic and it's probably the result of a database query. In other words, the controller of any page that displays that sidebar must make the same database query and pass the list of articles to the included template fragment.

The alternative solution proposed by Symfony is to create a controller that only displays the list of recent articles and then call to that controller from any template that needs to display that content.

First, create a controller that renders a certain number of recent articles:

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// src/AppBundle/Controller/ArticleController.php
namespace AppBundle\Controller;

// ...

class ArticleController extends Controller
{
    public function recentArticlesAction($max = 3)
    {
        // make a database call or other logic
        // to get the "$max" most recent articles
        $articles = ...;

        return $this->render(
            'article/recent_list.html.twig',
            array('articles' => $articles)
        );
    }
}

Then, create a recent_list template fragment to list the articles given by the controller:

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{# app/Resources/views/article/recent_list.html.twig #}
{% for article in articles %}
    <a href="{{ path('article_show', {slug: article.slug}) }}">
        {{ article.title }}
    </a>
{% endfor %}

Finally, call the controller from any template using the render() function and the common syntax for controllers (i.e. bundle:controller:action):

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{# app/Resources/views/base.html.twig #}

{# ... #}
<div id="sidebar">
    {{ render(controller(
        'AppBundle:Article:recentArticles',
        { 'max': 3 }
    )) }}
</div>

Whenever you find that you need a variable or a piece of information that you don't have access to in a template, consider rendering a controller. Make sure that embedded controllers are fast to execute to not hurt performance and that they follow Symfony's best practices for controllers.