Building a Custom Drupal 9 Module for API Integration: Storing API Key, Rendering REST API Responses with Twig

1. Module Creation:

   Create a custom module folder in the modules/custom directory. Let's name it custom_api_integration.

   mkdir modules/custom/custom_api_integration

2. Module Info File:

   Create custom_api_integration.info.yml to define module metadata.

   name: 'Custom API Integration'
   type: module
   description: 'Integrate with external API and render responses.'
   package: Custom
   core_version_requirement: ^8 || ^9
   package: Custom

3. Module File Structure:

   Organize module files:

   custom_api_integration/
   ├── config/
   │   └── install/
   │       └── custom_api_integration.settings.yml
   ├── src/
   │   ├── Controller/
   │   │   └── CustomApiController.php
   │   ├── Plugin/
   │   │   └── Block/
   │   │       └── CustomApiBlock.php
   │   └── PluginManager/
   │       └── CustomApiManager.php
   ├── templates/
   │   └── custom-api-block.html.twig
   ├── custom_api_integration.module
   └── custom_api_integration.install
   

4. Configuration Setting:

   Create custom_api_integration.settings.yml for storing API key.

   api_key: ''

5. Module Implementation:

   • custom_api_integration.module

     <?php
     
     /**
      * Implements hook_help().
      */
     function custom_api_integration_help($route_name, \Drupal\Core\Routing\RouteMatchInterface $route_match) {
       switch ($route_name) {
         case 'help.page.custom_api_integration':
           return '<p>' . t('Custom API Integration module provides API integration functionality.') . '</p>';
       }
     }

   • custom_api_integration.install

     <?php
     
     /**
      * Implements hook_install().
      */
     function custom_api_integration_install() {
       // Set default configuration values.
       \Drupal::configFactory()
         ->getEditable('custom_api_integration.settings')
         ->set('api_key', '')
         ->save();
     }

   • src/Plugin/Block/CustomApiBlock.php

     <?php
     
     namespace Drupal\custom_api_integration\Plugin\Block;
     
     use Drupal\Core\Block\BlockBase;
     
     /**
      * Provides a 'Custom API Block' block.
      *
      * @Block(
      *   id = "custom_api_block",
      *   admin_label = @Translation("Custom API Block"),
      * )
      */
     class CustomApiBlock extends BlockBase {
     
       /**
        * {@inheritdoc}
        */
       public function build() {
         $api_manager = \Drupal::service('custom_api_integration.manager');
         $api_response = $api_manager->getApiResponse();
         return [
           '#markup' => $api_response,
           '#cache' => [
             'max-age' => 0,
           ],
         ];
       }
     }

   • src/Controller/CustomApiController.php

     <?php
     
     namespace Drupal\custom_api_integration\Controller;
     
     use Drupal\Core\Controller\ControllerBase;
     
     /**
      * Class CustomApiController.
      */
     class CustomApiController extends ControllerBase {
     
       /**
        * {@inheritdoc}
        */
       public function content() {
         return [
           '#markup' => $this->t('Welcome to the Custom API Integration module.'),
         ];
       }
     }

   • src/PluginManager/CustomApiManager.php

     <?php
     
     namespace Drupal\custom_api_integration\PluginManager;
     
     use Drupal\Core\Plugin\PluginBase;
     
     /**
      * Provides a base class for Custom API Manager plugins.
      */
     abstract class CustomApiManager extends PluginBase {
     
       /**
        * Get API response.
        *
        * @return string
        *   The API response.
        */
       abstract public function getApiResponse();
     }

6. Twig Template:

   Create custom-api-block.html.twig in the templates folder.

   <div class="custom-api-block">  {{ content }} </div>

7. Service Definition:

   Define the service in custom_api_integration.services.yml.

   services:
     custom_api_integration.manager:
       class: Drupal\custom_api_integration\PluginManager\CustomApiManager
       arguments: ['@config.factory']
       abstract: true
       shared: false

8. Custom API Manager Implementation:

   Create a custom API manager plugin that extends CustomApiManager.

   • src/PluginManager/CustomApiManagerImpl.php

     <?php
     
     namespace Drupal\custom_api_integration\PluginManager;
     
     use Drupal\Core\Config\ConfigFactoryInterface;
     use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
     use Drupal\Core\Plugin\PluginFormInterface;
     use Drupal\Core\Plugin\PluginManagerInterface;
     use Drupal\Core\Plugin\PluginBase;
     use Symfony\Component\DependencyInjection\ContainerInterface;
     
     /**
      * Provides a 'Custom API Manager' plugin.
      *
      * @Plugin(
      *   id = "custom_api_manager_impl",
      *   label = @Translation("Custom API Manager Implementation"),
      * )
      */
     class CustomApiManagerImpl extends CustomApiManager implements ContainerFactoryPluginInterface, PluginFormInterface {
     
       /**
        * Config Factory.
        *
        * @var \Drupal\Core\Config\ConfigFactoryInterface
        */
       protected $configFactory;
     
       /**
        * {@inheritdoc}
        */
       public function __construct(array $configuration, $plugin_id, $plugin_definition, ConfigFactoryInterface $config_factory) {
         parent::__construct($configuration, $plugin_id, $plugin_definition);
         $this->configFactory = $config_factory;
       }
     
       /**
        * {@inheritdoc}
        */
       public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
         return new static(
           $configuration,
           $plugin_id,
           $plugin_definition,
           $container->get('config.factory')
         );
       }
     
       /**
        * {@inheritdoc}
        */
       public function getApiResponse() {
         // Implement API call logic using stored API key.
         $api_key = $this->configFactory->get('custom_api_integration.settings')->get('api_key');
         // Make API request and handle response.
         // ...
     
         return 'API Response Placeholder';
       }
     }

9. Enable the Module:

   Enable the module using Drush or the Drupal UI.

   drush en custom_api_integration

This is a basic structure to get you started. Adjust and expand based on your specific API integration requirements. Ensure you replace placeholder comments with actual implementation details.