4.2-custom-modules.md

Custom Modules

To illustrate the module creation process, you can follow along with the following instructions on this page to create a custom module called hello_world (adapted from Creating Custom Modules).

Create Module Skeleton

Naming Your Module

From Naming and placing your Drupal 8 module:

There are some important rules to follow when selecting a machine name:

• It must start with a letter.
• It must contain only lower-case letters and underscores.
• It must not contain any spaces.
• It must be unique. Your module may not have the same short name as any other module, theme, or installation profile you will be using on the site.
• It may not be any of the reserved terms : src, lib, vendor, assets, css, files, images, js, misc, templates, includes, fixtures, Drupal.

For example: hello_world

Once you've selected a machine name, create a new directory for your module inside /modules/. It is recommended to use your machine name, but not required.

For example: /modules/hello_world

{modulename}.info.yml

By creating a {modulename}.info.yml inside your module, you notify Drupal that your module exists.

For example - hello_world.info.yml:

name: Hello World Module
description: Creates a page showing "Hello World".
package: Custom

type: module
core: 8.x

Module Keys

The following keys are available for modules:

• name (required) - The human-readable name. This will appear on the "Extend" page where the module is activated.
• type (required) - Indicates the type of extension, i.e., "module", "theme", or "profile". For modules this should always be set to "module".
• description (optional) - The description, displayed on the "Extend" page.
• package (optional) - Specifies a "package" that allows you to group modules together.
• core (required) - Specifies the version of Drupal core that the theme/module is compatible with.
• php (optional) - The minimum version of PHP required. Defaults to value of DRUPAL_MINIMUM_PHP constant.
• version (optional) - Specifies a version. For modules hosted on drupal.org, the version number will be filled in by the packaging script. Do not specify it manually, but leave out the version line entirely.
• libraries (optional) - A list of libraries (which can contain both CSS and JavaScript assets) to add to all pages where the module is active.
• dependencies (optional) - List of other modules a module is dependent upon.
• test_dependencies (optional) - List of other modules a module is dependent upon for testing purposes. Test dependencies should be added and committed to your repo prior to writing tests that rely on those dependencies so that testbot can properly download them.
• hidden (optional) - Indicates whether or not to hide the module from the "Extend" page so that it cannot be enabled/disabled via the UI.

Adding a Controller

Module controllers should live inside src/Controller directory inside your module.

For example - src/Controller/HelloController.php:

<?php

namespace Drupal\hello_world\Controller;

use Drupal\Core\Controller\ControllerBase;

class HelloController extends ControllerBase {

  /**
   * Display the markup.
   *
   * @return array
   */
  public function content() {
    return [
      '#type' => 'markup',
      '#markup' => $this->t('Hello, World!'),
    ];
  }

}

This example controller simply returns a render array containing the translatable string 'Hello, World!'.

Adding a Route

Next you can add a route, exposing the controller's content via URL.

For example - hello_world.routing.yml:

hello_world.content:
  path: '/hello'
  defaults:
    _controller: '\Drupal\hello_world\Controller\HelloController::content'
    _title: 'Hello World'
  requirements:
    _permission: 'access content'

After adding this route, clear your cache and then navigate to /hello in your browser to see the controller's returned content.

See Essential APIs: Routing System for more details about the Drupal 8 routing system.

Adding a Menu Link

Next you can add a link for this module page under Configuration -> Development in the admin panel.

For example - hello_world.links.menu.yml:

hello_world.admin:
  title: 'Hello module settings'
  description: 'example of how to make an admin settings page link'
  parent: system.admin_config_development
  route_name: hello_world.content
  weight: 100

See Essential APIs: Menu API for more details about the Menu API.

Additional Resources

• drupal.org - Creating Custom Modules
• drupal.org - Naming and placing your Drupal 8 module

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