Grouped checkboxes in Symfony / twig - symfony

Question

I have 2 entities: Projects and Categories. I have a ManyToMany relation between these two.
The Categories has ManytoOne relation with the entity "industry"
At this moment, there is no direct relation between Projects and industry and I would like to keep this like so, for further search functionality. So in the category table, the list includes categories from all industries.
When I build the form to edit the project (using the form widget), I have a list of checkboxes representing all the categories listed in my category table.
I would like to group the category choices by industry. How can this be done on the form layout only? How can I extract the industry value from the twig widget form data and group the checkboxes by the industry entity?

Answer 1

Thanks Leevi,
I could not find how to implement the suggestion above using both industry and category related entities... I finally found this way of going around the issue, tell me if there is a simpler way, but this works perfect now.
This is my form in the controller
$form = $this->createFormBuilder($project)
->add('categories', 'entity', array(
'class' => 'ACMEProjectBundle:Category',
'property' => 'name',
'expanded' => true,
'multiple' => true,
->getForm();
I also pass to the rendered form the array of industries which has each a list of related categories
$industries = $this->getDoctrine()->getManager()->getRepository('ACMEProjectBundle:Industry')->findall();
In the form.html.twig template
{{ form_errors(form) }}
<form method="post" {{ form_enctype(form) }}>
{% for industry in industries %}
<h4>{{industry.name}}</h4>
<ul class="unstyled">
{% for category in industry.categories %}
{% set key = category.id %}
<li>{{ form_widget(form.categories[key]) }}{{category.name}}</li>
{% endfor %}
</ul>
{% endfor %}
{{form_rest(form)}}
Which gives me the wanted results.

Answer 2

Hopefully this will be enough direction without giving you exact code examples :).
You'll have to setup your form with an expanded, multiple, entity field like so:
<?php
// src/Acme/ProjectBundle/Controller/DefaultController.php
namespace Acme\ProjectBundle\Controller;
use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Acme\ProjectBundle\Entity\Project;
use Symfony\Component\HttpFoundation\Request;
class DefaultController extends Controller
{
public function newAction(Request $request)
{
// create a project and give it some dummy data for this example
$project = new Project();
$form = $this->createFormBuilder($project)
->add('categories', 'entity', array(
'expanded' => true,
'multiple' => true,
'group_by' => 'industry.title'
))
->add('save', 'submit')
->getForm();
return $this->render('AcmeProjectBundle:Default:new.html.twig', array(
'form' => $form->createView(),
));
}
}
The group_by parameter groups the options based on the property path:
See: http://symfony.com/doc/current/reference/forms/types/entity.html#group-by
Now group_by renders a select tag but you should be able to override that with a custom twig theme or manually in the template.
Given the form above you can access the choices in {{ form.categories.vars.choices }} and iterate over them manually.
See: {% block choice_widget_collapsed %} in form_div_layout.html.twig to see how the select box is rendered.
Here's some more information of form theming: http://symfony.com/doc/current/cookbook/form/form_customization.html