Book Image

Mastering Drupal 8

By : Sean Montague, Chaz Chumley, William Hurley
Book Image

Mastering Drupal 8

By: Sean Montague, Chaz Chumley, William Hurley

Overview of this book

Drupal is an open source content management system trusted by governments and organizations around the globe to run their websites. It brings with it extensive content authoring tools, reliable performance, and a proven track record of security. The community of more than 1,000,000 developers, designers, editors, and others have developed and maintained a wealth of modules, themes, and other add-ons to help you build a dynamic web experience. Drupal 8 is the latest release of the Drupal built on the Symfony2 framework. This is the largest change to the Drupal project in its history. The entire API of Drupal has been rebuilt using Symfony and everything from the administrative UI to themes to custom module development has been affected. This book will cover everything you need to plan and build a complete website using Drupal 8. It will provide a clear and concise walkthrough of the more than 200 new features and improvements introduced in Drupal core. In this book, you will learn advanced site building techniques, create and modify themes using Twig, create custom modules using the new Drupal API, explore the new REST and Multilingual functionality, import, and export Configuration, and learn how to migrate from earlier versions of Drupal.
Table of Contents (25 chapters)
Title Page
Credits
About the Author
Acknowledgments
About the Author
About the Reviewer
Customer Feedback
www.PacktPub.com
Preface

The role of the theme file in Drupal


Themes can be simple to compose, sometimes containing a single configuration file, a couple of Twig templates, and a few assets. However, there will be times when we need to intercept and override variables and data that Drupal outputs before they reach our Twig templates.

Drupal's API (https://api.drupal.org/api/drupal/8) allows us to create a *.theme file where we can add theme functions that can hook into the API using different types of function calls:

  • Preprocess: This is a set of function calls specific to different templates that allow us to manipulate variables before they are output to the page
  • Hooks: This is a set of function calls to hook into the Drupal API that allows us to alter variables and override default implementations

Preprocessors and hooks

The main role of preprocessor functions is to prepare variables to be used within our Twig templates using template_preprocess functions. These functions reference the theme and template we want to...