Symfony twig how to add class to a form row

Question

I am building a project in Symfony 2.3 using Twig. I want to add a class to the form row block. I am using a form theme file which contains:

{% block form_row %}
    <div class="form-row">
        {{ form_label(form) }}
        {{ form_widget(form) }}
        {{ form_errors(form) }}
    </div>
{% endblock %}

Now some of my form rows I want to add an extra class form-row-split. I can't figure out how to do this properly. The way I have it almost-working is:

{% block form_row %}
    {% set attr = attr|merge({'class': 'form-row' ~ (attr.class is defined ? ' ' ~ attr.class : '') ~ (errors|length > 0 ? ' error' : '')} ) %}
    <div {{ block('widget_container_attributes') }}>
        {{ form_label(form) }}
        {{ form_widget(form) }}
        {{ form_errors(form) }}
    </div>
{% endblock %}

(Note, I've left the error class logic in there too as that needs to stay). Then in the form builder:

$builder
        ->add('first_name', 'text', array(
            'attr' => array(
                'class' => 'form-row-split'
            )
        ));

This almost works but it adds this class everywhere and also adds the widget id to the row!

<div id="myform_first_name" class="form-row form-row-split">
    <label for="myform_first_name">First name</label>
    <input id="myform_first_name" class="form-row-split" type="text" name="myform[first_name]">
</div>

I can think of a few potential solutions but none of them are pretty or straight forward. Surely there must be a simple way of doing this?

Answer 1

There is a fairly simple solution to this problem actually. I just needed a form type extension to extend the base form type to allow an extra available option: http://symfony.com/doc/2.3/cookbook/form/create_form_type_extension.html

Following through the example in the docs, I created a new form type extension:

// src/Acme/FrontendBundle/Form/Extension/FormTypeExtension.php

namespace Acme\FrontendBundle\Form\Extension;

use Symfony\Component\Form\AbstractTypeExtension;
use Symfony\Component\Form\FormInterface;
use Symfony\Component\Form\FormView;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;

/**
 * Class FormTypeExtension
 * @package Acme\FrontendBundle\Form\Extension
 */
class FormTypeExtension extends AbstractTypeExtension
{
    /**
     * Extends the form type which all other types extend
     *
     * @return string The name of the type being extended
     */
    public function getExtendedType()
    {
        return 'form';
    }

    /**
     * Add the extra row_attr option
     *
     * @param OptionsResolverInterface $resolver
     */
    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
            'row_attr' => array()
        ));
    }

    /**
     * Pass the set row_attr options to the view
     *
     * @param FormView $view
     * @param FormInterface $form
     * @param array $options
     */
    public function buildView(FormView $view, FormInterface $form, array $options)
    {
        $view->vars['row_attr'] = $options['row_attr'];
    }
}

Then I registered the service in my bundle...

<!-- Form row attributes form extension -->
<service id="acme.form_type_extension" class="Acme\FrontendBundle\Form\Extension\FormTypeExtension">
    <tag name="form.type_extension" alias="form" />
</service>

Since every widget extends the base form type this then allows me to pass this new row_attr option through on any field, eg:

$builder
    ->add('first_name', 'text', array(
        'row_attr' => array(
            'class' => 'form-row-split'
        )
    ));

Then the twig overrides to make use of the new row_attr option:

{% block form_row %}
    <div {{ block('form_row_attributes') }}>
        {{ form_label(form) }}
        {{ form_widget(form) }}
        {{ form_errors(form) }}
    </div>
{% endblock form_row %}

{% block form_row_attributes %}
    {% spaceless %}
        {% for attrname, attrvalue in row_attr %}{{ attrname }}="{{ attrvalue }}" {% endfor %}
    {% endspaceless %}
{% endblock form_row_attributes %}

And it's done!

(For completeness, my full twig override still merges in the form-row and error classes in like so:

{% set row_attr = row_attr|merge({'class': 'form-row' ~ (row_attr.class is defined ? ' ' ~ row_attr.class : '') ~ (errors|length > 0 ? ' error' : '')} ) %}

.. but thats not really necessary for answering my own question :P )