HtmxTestAjaxForm.php

<?php

declare (strict_types=1);
namespace Drupal\test_htmx\Form;

use Drupal\Core\Form\FormBase;
use Drupal\Core\Form\FormStateInterface;
use Drupal\test_htmx\Controller\HtmxTestAttachmentsController;

/**
 * A small form used to insert an HTMX powered element using ajax API.
 */
class HtmxTestAjaxForm extends FormBase {
  
  /**
   * {@inheritdoc}
   */
  public function getFormId() : string {
    return 'htmx_test_ajax_form';
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state) : array {
    $build = [
      'ajax-button' => [
        '#type' => 'button',
        '#value' => 'Trigger Ajax',
        '#submit_button' => FALSE,
        '#ajax' => [
          'callback' => [
            HtmxTestAttachmentsController::class,
            'replaceWithAjax',
          ],
          'wrapper' => 'ajax-test-container',
        ],
      ],
      '#suffix' => '<div id="ajax-test-container"></div>',
    ];
    return $build;
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) : void {
  }

}