What are preprocess hook in Drupal8?

What are preprocess hook in Drupal8?

What Are Preprocess Functions? for Drupal 8, Drupal 9. Preprocess functions allow Drupal themes to manipulate the variables that are used in Twig template files by using PHP functions to preprocess data before it is exposed to each template.

What is Drupal hook?

Hooks allow modules to alter and extend the behavior of Drupal core, or another module. They are one of the various ways that code components in Drupal can communicate with one another. Using hooks a module developer can change how core or another module works — without changing the existing code.

What is a theme hook?

A theme hook suggestion is an alternate template (. tpl. php) file that you have created to override the base or original template file.

How module hooks will be called?

From an implementation perspective hooks are specially-named functions called at specific times to alter or add to the base behavior. Each hook has a unique name (e.g., hook_entity_load() ), a defined set of parameters, and a defined return value. Any number of modules can implement the same hook. …

When to use theme preprocess hook in Drupal?

Preprocess theme variables for a specific theme hook. This hook allows modules to preprocess theme variables for a specific theme hook. It should only be used if a module needs to override or add to the theme preprocessing for a theme hook it didn’t define. For more detailed information, see the Theme system overview topic.

How to preprocesse attributes in a.theme file?

You could inspect the $variables object with a condition to determine which menu you are working with. The elements within $variables become available in twig after theme Pre-Processing. So now to extend our example, let’s assume we want to add the class “my-main-menu” to the main menu of your site.

How to create a preprocess function in twig?

To work with preprocess functions: Create a function such as mytheme_preprocess_HOOK where HOOK refers to the item you wish to affect * Rebuild the cache so your changes are available (if you have drush installed, drush cr on the command line) * HOOK names follow twig template suggestions.

How to create a hook for page.html?

To create a hook for page. html. twig you create mytheme_preprocess_page. To create a hook for node — article. html. twig you create mytheme_preprocess_node__article (replacing dashes with underscores). To discover hook names, see Locating Template Files with Debugging.