How to Create a Custom Form Field Type

Defining the Field Type

In order to create the custom field type, first you have to create the class representing the field. In this situation the class holding the field type will be called ShippingType and the file will be stored in the default location for form fields, which is <BundleName>\Form\Type.

All field types must implement the FormTypeInterface, but you should instead extend from AbstractType, which already implements that interface and provides some utilities:

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// src/AppBundle/Form/Type/ShippingType.php
namespace AppBundle\Form\Type;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\Extension\Core\Type\ChoiceType;
use Symfony\Component\OptionsResolver\OptionsResolver;

class ShippingType extends AbstractType
{
    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefaults([
            'choices' => [
                'Standard Shipping' => 'standard',
                'Expedited Shipping' => 'expedited',
                'Priority Shipping' => 'priority',
            ],
            'choices_as_values' => true,
        ]);
    }

    public function getParent()
    {
        return ChoiceType::class;
    }
}

Here, the return value of the getParent() function indicates that you're extending the ChoiceType field. This means that, by default, you inherit all of the logic and rendering of that field type. To see some of the logic, check out the ChoiceType class.

There are three methods that are particularly important:

buildForm()

Each field type has a buildForm() method, which is where you configure and build any field(s). Notice that this is the same method you use to setup your forms, and it works the same here.

buildView()

This method is used to set any extra variables you'll need when rendering your field in a template. For example, in ChoiceType, a multiple variable is set and used in the template to set (or not set) the multiple attribute on the select field. See Creating a Template for the Field for more details.

configureOptions()

This defines options for your form type that can be used in buildForm() and buildView(). There are a lot of options common to all fields (see FormType Field), but you can create any others that you need here.

The goal of this field was to extend the choice type to enable selection of the shipping type. This is achieved by fixing the choices to a list of available shipping options.

Creating a Template for the Field

Each field type is rendered by a template fragment, which is determined in part by the class name of your type. For more information, see How to Customize Form Rendering.

In this case, since the parent field is ChoiceType, you don't need to do any work as the custom field type will automatically be rendered like a ChoiceType. But for the sake of this example, suppose that when your field is "expanded" (i.e. radio buttons or checkboxes, instead of a select field), you want to always render it in a ul element. In your form theme template (see above link for details), create a shipping_widget block to handle this:

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{# app/Resources/views/form/fields.html.twig #}
{% block shipping_widget %}
    {% spaceless %}
        {% if expanded %}
            <ul {{ block('widget_container_attributes') }}>
            {% for child in form %}
                <li>
                    {{ form_widget(child) }}
                    {{ form_label(child) }}
                </li>
            {% endfor %}
            </ul>
        {% else %}
            {# just let the choice widget render the select tag #}
            {{ block('choice_widget') }}
        {% endif %}
    {% endspaceless %}
{% endblock %}

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# app/config/config.yml
twig:
    form_themes:
        - 'form/fields.html.twig'

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<!-- app/config/config.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:twig="http://symfony.com/schema/dic/twig"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        https://symfony.com/schema/dic/services/services-1.0.xsd
        http://symfony.com/schema/dic/twig
        https://symfony.com/schema/dic/twig/twig-1.0.xsd">

    <twig:config>
        <twig:form-theme>form/fields.html.twig</twig:form-theme>
    </twig:config>
</container>

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// app/config/config.php
$container->loadFromExtension('twig', [
    'form_themes' => [
        'form/fields.html.twig',
    ],
]);

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# app/config/config.yml
framework:
    templating:
        form:
            resources:
                - ':form:fields.html.php'

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<!-- app/config/config.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:framework="http://symfony.com/schema/dic/symfony"
    xsi:schemaLocation="http://symfony.com/schema/dic/services https://symfony.com/schema/dic/services/services-1.0.xsd
    http://symfony.com/schema/dic/symfony https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">

    <framework:config>
        <framework:templating>
            <framework:form>
                <framework:resource>:form:fields.html.php</twig:resource>
            </framework:form>
        </framework:templating>
    </framework:config>
</container>

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// app/config/config.php
$container->loadFromExtension('framework', [
    'templating' => [
        'form' => [
            'resources' => [
                ':form:fields.html.php',
            ],
        ],
    ],
]);

Using the Field Type

You can now use your custom field type by creating a new instance of the type in one of your forms:

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// src/AppBundle/Form/Type/OrderType.php
namespace AppBundle\Form\Type;

use AppBundle\Form\Type\ShippingType;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;

class OrderType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add('shippingCode', ShippingType::class, [
            'placeholder' => 'Choose a delivery option',
        ]);
    }
}

But this only works because the ShippingType() is very simple. What if the shipping codes were stored in configuration or in a database? The next section explains how more complex field types solve this problem.

Accessing Services and Config

If you need to access services from your form class, add a __construct() method like normal:

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// src/AppBundle/Form/Type/ShippingType.php
namespace AppBundle\Form\Type;

// ...
use Doctrine\ORM\EntityManagerInterface;

class ShippingType extends AbstractType
{
    private $entityManager;

    public function __construct(EntityManagerInterface $entityManager)
    {
        $this->entityManager = $entityManager;
    }

    // use $this->entityManager down anywhere you want ...
}

If you're using the default services.yml configuration (i.e. services from the Form/ are loaded and autoconfigure is enabled), this will already work! See Service Container for more details.

Have fun!