Using formBuilder service to render formsfor Drupal 8 , 9 , 10 , and 11

In this lesson, we enhance our understanding of developing Drupal forms by exploring the formBuilder service. With the formBuilder service, you can efficiently render forms, making them dynamic and reusable across your Drupal site.

Understanding the formBuilder Service

The formBuilder service is a part of Drupal's core that manages the reading, assembling, and displaying of forms. It's integral for handling forms programmatically, allowing developers to build, invoke, and render forms wherever needed within custom code, such as controllers, routes, and even blocks.

Why Use the formBuilder Service?

Utilizing the formBuilder service offers several advantages:

• Flexibility: It allows the rendering of forms independently of static paths or direct callbacks.
• Reusability: The same form logic can be used with different tokens, arguments, or settings across various site sections.
• Consistency: Ensures all forms follow Drupal's theming, validation, and submission standards.

Implementing the formBuilder Service

The formBuilder service provides methods to create and manage forms on your Drupal site programmatically.

Using formBuilder in Controllers

To effectively use the formBuilder service, you will often work within custom module controllers. Here’s a quick step-by-step guide on implementing this:

1. Ensure your custom module is enabled.
2. Create a controller within your module's src/Controller directory. For example, create a file named CustomFormController.php and define the following:

namespace Drupal\my_custom_form\Controller;

use Drupal\Core\Controller\ControllerBase;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Drupal\Core\Form\FormBuilderInterface;

class CustomFormController extends ControllerBase {
    
    protected $formBuilder;
    
    public function __construct(FormBuilderInterface $form_builder) {
        $this->formBuilder = $form_builder;
    }

    public static function create(ContainerInterface $container) {
        return new static(
            $container->get('form_builder')
        );
    }

    public function displayForm() {
        return $this->formBuilder->getForm('Drupal\my_custom_form\Form\CustomForm');
    }
}

    

Routing to the Controller

To make the form accessible, define a route in the my_custom_form.routing.yml file:

my_custom_form.display:
  path: '/custom-form-page'
  defaults:
    _controller: '\Drupal\my_custom_form\Controller\CustomFormController::displayForm'
    _title: 'My Custom Form'
  requirements:
    _permission: 'access content'

    

How formBuilder Works

Inside the Controller

The controller accesses the formBuilder service via dependency injection, as shown in the create() method. This method is recommended by Drupal to ensure all dependencies are managed effectively.

The displayForm() method uses the getForm() method of the formBuilder service, referencing the fully qualified namespace of your form class (e.g., Drupal\my_custom_form\Form\CustomForm).

Benefits of This Approach

Separation of Concerns

Keeping form processing logic separate from application flow and logic makes for cleaner, more maintainable code.

Centralized Form Management

Forms are managed centrally, reducing the risk of duplicated logic. This streamlines your workflow and enhances site performance.

Summary

In this lesson, we examined how the formBuilder service is used to render Drupal forms programmatically. Employing this service allows you to create highly reusable and organized form logic that enhances flexibility and scalability.

Next Steps

As we continue our series, our next lesson will tackle "Displaying forms via routes or blocks". In this future session, you'll explore additional methods of presenting forms dynamically on your Drupal site, further broadening your form display options and capabilities.