Create a simple module to use Drupal 8 Hook System | Drupal 8

Create a simple module to use Drupal 8 Hook System

Submitted by editor on Fri, 07/08/2016 - 10:58

What are the drupal hooks and how to use drupal hooks ?

Drupal 8 Hook System

Hooks allow modules to alter the drupal core behavior or another module. Hooks are discovered and called at specific times to alter or add to the base behavior or data (invoking the hook). Each hook has a name start with hook_ (Ex; hook_menu()). Your modules can also define their own hooks, in order to let other modules interact with them.

How to use drupal hooks ?

1. Create a custom module (See Create a simple module).
Hire module name is 'test'

2. Add a php file with .module extention at the root of the module called THEMODULENAME.module
Hire File name is test.module

3. Now you can implement any drupal 8 hook in this file

To implement a hook, you must replace hook_ by YourModuleName_. Ex hook_help() become test_help()

Example: Implement hool_help();

 * Implements hook_help().
 * Displays help and module information.
 * @param path
 *   Which path of the site we're using to display help
 * @param arg
 *   Array that holds the current path as returned from arg() function
function test_help($path, $arg) {
  switch ($path) {
    case "":
      return '' . t("Hello, This is my first hook") . '';

4. Then Visit /admin/help/test to Test your Hook
If you can see the message "Hello, This is my first hook", it's work.


More about Extending and altering Drupal :


Jim (not verified)

Thu, 06/15/2017 - 16:08

I have the following file named background_image_style.module 

In my drupal 8.3.3 site the paragraphs.module is at...

I installed the site and all contributed modules with Composer...

composer require drupal/paragraphs
vendor\bin\drupal module:install paragraphs

My question is... Where does the hook module go? Does it need to be installed with Composer (I just copied it in where paragraphs.module is) Are there any other overhead steps that needs to be done? (editing other files?)

I tried several locations and cleared all caches each time. Thanks for any help or ideas!

* Implements paragraphs().
function background_image_style_preprocess_paragraph__banner(&$variables) {
  $paragraph = $variables['paragraph'];
  if (!$paragraph->field_image->isEmpty()) {
    $image = $paragraph->field_image->entity->url();
    $variables['attributes']['style'][] = 'background-image: url("' . $image . '");';
    $variables['attributes']['style'][] = 'background-size: cover;';
    $variables['attributes']['style'][] = 'background-position: center center;';

Adam Borecki (not verified)

Tue, 10/03/2017 - 02:20

This is extremely helpful, super easy to follow and exactly what I needed. Much better than the actual drupal8 documentation.

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