Book Image

Drupal 8 Development Cookbook - Second Edition

By : Matt Glaman
Book Image

Drupal 8 Development Cookbook - Second Edition

By: Matt Glaman

Overview of this book

Began as a message board, Drupal today is open source software maintained and developed by a community of over 1,000,000 users and developers. Drupal is used by numerous local businesses to global corporations and diverse organizations all across the globe. With Drupal 8’s exciting features it brings, this book will be your go-to guide to experimenting with all of these features through helpful recipes. We’ll start by showing you how to customize and configure the Drupal environment as per your requirements, as well as how to install third-party libraries and then use them in the Drupal environment. Then we will move on to creating blocks and custom modules with the help of libraries. We will show you how to use the latest mobile-first feature of Drupal 8, which will help you make your apps responsive across all the major platforms. This book will also show you how to incorporate multilingual facilities in your sites, use web services and third-party plugins with your applications from inside Drupal 8, and test and deploy your apps.
Table of Contents (20 chapters)
Title Page
About the Author
About the Reviewer
Customer Feedback

Altering other forms

Drupal's Form API does not just provide a way to create forms. There are ways to alter forms through a custom module that allows you to manipulate the core and contributed forms. Using this technique, new elements can be added, default values can be changed, or elements can even be hidden from view to simplify the user experience.

The altering of a form does not happen in a custom class; this is a hook defined in the module file. In this recipe, we will use the hook_form_FORM_ID_alter() hook to add a telephone field to the site's configuration form.

Getting ready

This recipe assumes that you have a custom module to add the code to.

How to do it...

  1. In the modules folder of your Drupal site, create a folder named mymodule.
  1. In the mymodule folder, create a, containing the following code:
name: My module 
description: Custom module that uses a form alter 
type: module 
core: 8.x 
  1. Next, create a mymodule.module file in your module's directory: