Creating a Custom Module in Drupal 8: A Comprehensive Guide

Drupal 8 has undergone significant changes in its module structure, making it important to understand the new directory and file structures, as well as the steps to create a custom module. This guide walks you through the process of creating a custom module in Drupal 8, from setting up the directory structure to defining routes and implementing the module functionalities.

Step 1: File Structure

In Drupal 8, custom or contributed modules should be placed under the modules folder in the root directory. For a custom module, the structure would look like:

modules/contrib/modules/custom/my_custom_module/

For multisite configurations, the modules should be placed in the sites directory:

sites/your_site_name_1/modules/sites/your_site_name_2/modules/

Step 2: Create .info.yml File

The .info file in Drupal 8 has been converted to .info.yml. This file contains metadata about the module, such as its name, description, package, and compatibility with Drupal core.

name: My Custom Moduletype: moduledescription: 'Example for Drupal 8 modules.'package: Customversion: 8.xcore: 8.x

Step 3: Creating .routing.yml

The routing system in Drupal 8 relies on the Symfony2 components. The routing file defines the routes and maps them to controller methods. Here is an example of a .routing.yml file:

_page:  path: /mypage/page  defaults:    _controller: DrupalexampleControllerExampleController::myPage    _title: 'My first page in Drupal8'  requirements:     _permission: 'access content'

The first line is the route, which is a machine name. Under path, we define the URL of the route. Under defaults, we specify the default page title and the controller method. Under requirements, we define the permissions the user must have to access the route.

Step 4: Create Route Controller Class

The controller class is where the business logic resides. It must follow the PSR-4 naming standard. Here is an example of the controller class:

use DrupalCoreControllerControllerBase;namespace DrupalexampleController;/** * Provides route responses for the Example module. */class ExampleController extends ControllerBase {  /**   * Returns a simple page.   *   * @return array   *   A simple renderable array.   */  public function myPage() {    $elements  [];    $elements['markup']  $this-t('Hello world!');    return $elements;  }}

The controller class extends DrupalCoreControllerControllerBase. The myPage method is the method that will be called when the specified route is accessed. It constructs and returns a renderable array.

Step 5: Creating .module and hook_menu

The hook_menu function is used to define menu items, which should match the paths and route names defined in the .routing.yml file. Here is an example of a .module file:

Here, we define a menu item that maps to the myPage method in the controller. The page callback sets the route to use the myPage method, and the access arguments define the required permissions.

Conclusion

Coding a custom module in Drupal 8 requires a good understanding of the new module lifecycle, routing system, and the PSR-4 naming standard. By following the steps outlined in this guide, you can successfully create a custom module that integrates seamlessly with the Drupal 8 framework.