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Drupal 8 Module Development
Drupal 8 Module Development

Drupal 8 Module Development: Build modules and themes using the latest version of Drupal 8 , Second Edition

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Drupal 8 Module Development

Creating Your First Module

Now that we have covered some of the introductory aspects of Drupal 8 module development, it's time to dive right into the meat of what we are doing here—module creation.

Here are some of the important topics that we will cover in this chapter:

  • Creating a new Drupal 8 module—the files that are necessary to get started
  • Creating a route and controller
  • Creating and using a service
  • Creating a form
  • Creating a custom block
  • Working with links
  • Using the Event Dispatcher

Concretely, in this chapter, we will create a new custom module called Hello World. In this module, we will define a route that maps to a Controller and that outputs the age-old programming message. So, this will be our first win.

Next, we will define a service that our Controller will use to pimp up our message. After all, we don't want the same message presented to...

Creating a module

Creating a simple Drupal 8 module is not difficult. You only need one file to get it recognized by the core installation and to be able to enable it. In this state, it won't do much, but it will be installable. Let's first take a look at how to do this, and then we will progressively add meat to it in order to achieve the goals set out at the beginning of the chapter.

Custom Drupal 8 modules typically belong inside the /custom directory of the /modules folder found inside the root Drupal installation. You would put contributed modules inside a /contrib directory instead, in order to have a clear distinction. This is a standard practice, so that is where we will place our custom module, called Hello World.

We will start by creating a folder called hello_world. This will also be the module's machine name used in many other places. Inside, we will...

Using services in Drupal 8

Before we go and use our service in the Controller we created, let's take a breather and run through the ways you can make use of services once they are registered.

There are essentially two ways—statically and injected. The first is done by a static call to the Service Container, whereas the second uses dependency injection to pass the object through the constructor (or in some rare cases, a setter method). However, let's check out how, why, and what is the real difference.

Statically, you would use the global Drupal class to instantiate a service:

$service = \Drupal::service('hello_world.salutation');  

This is how we use services in the .module files and classes which are not exposed to the Service Container and into which we cannot inject. Instances of the latter are rare though, most of the time we use the static calls...

The form

Our page displays a greeting dynamically, depending on the time of day. However, we now want an administrator to specify what the greeting should actually be, in other words, to override the default behavior of our salutation if they so choose.

The ingredients for achieving this will be as follows:

  • A route (a new page) that displays a form where the administrator can set the greeting
  • A configuration object that will store the greeting

In building this functionality, we will also take a look at how to add a dependency to our existing service. So, let's get started with our new route that naturally goes inside the hello_world.routing.yml file we already created:

hello_world.greeting_form:
path: '/admin/config/salutation-configuration'
defaults:
_form: '\Drupal\hello_world\Form\SalutationConfigurationForm'
_title: 'Salutation configuration...

Blocks

Blocks in Drupal 8 are plugins. However, the blocks you create in the UI are content entities and the placement of both in the block layout are configuration entities. So, the block system is a good example of how entities and plugins work hand in hand in Drupal 8. We will talk in more detail about plugin types and entities later in the book.

The block system in Drupal 8 is a great shift from its predecessor. Before, you had to implement two obligatory hooks plus two optional hooks if you wanted the block to have a configuration, and the latter was always saved somewhere that had nothing to do with the block itself. In Drupal 8, we work with a simple plugin class that can be made container-aware (that is, we can inject dependencies into it) and we can store configuration in a logical fashion.

So, how do we create a custom block plugin? All we need is one class, placed in...

Working with links

One of the principal characteristics of a web application is the myriad of links between its resources. They are in fact the glue that brings it together. So, in this section, I want to show you a few common techniques used while working with links programmatically in Drupal 8.

There are two main aspects when talking about link building in Drupal—the URL and the actual link tag itself. So, creating a link involves a two-step process, but can also be shortened into a single call via some helper methods.

The URL

URLs in Drupal 8 are represented with the Drupal\Core\Url class, which has a number of static methods that allow you to create an instance. The most important of these is ::fromRoute(), which...

Event Dispatcher and redirects

A common thing you'll have to do as a module developer is to intercept a given request and redirect it to another page, and more often than not, this will have to be dynamic, depending on the current user or other contextual info. Drupal 7 developers know very well that this has always been an easy task. Simply implement hook_init(), which gets called on each request and then use the famous drupal_goto() function. This, however, is no longer the case in Drupal 8. What we have to do now is subscribe to the kernel.request event (remember this from the preceding chapter?) and then change the response directly. However, before seeing an example of this, let's take a look at how we can perform a simpler redirect from within a Controller. You know, since we're on the subject.

...

Summary

In this chapter, we covered a great deal of info about the things you need to know when developing Drupal 8 modules. The first thing we did was create our very own module skeleton that can be installed on a Drupal 8 site. Then, we saw how to create a new page at a specific path (route) and show some basic data on that page. Nothing too complex, but enough to illustrate one of the most common tasks you will do as a module developer. We then took that to a new level and abstracted the logic for that data calculation into a service. Not only that, but we also saw how we can use that service and, more importantly, how we should use it. Next, we saw how we can work with the Form API in Drupal 8 to allow administrators to add some configuration to the site. A very important takeaway here was also that the Form API page in Drupal 8 will prove invaluable because you have many...

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Key benefits

  • Explore a plethora of Drupal 8 APIs and get the best out of them using the power of PHP coding
  • Learn to implement efficient data management and data security by creating dedicated modules for it.
  • Stay up to date with the changes introduced in the new Drupal 8 releases

Description

Drupal 8 comes with a release cycle that allows for new functionality to be added at a much faster pace. However, this also means code deprecations and changing architecture that you need to stay on top of. This book updates the first edition and includes the new functionality introduced in versions up to, and including 8.7. The book will first introduce you to the Drupal 8 architecture and its subsystems before diving into creating your first module with basic functionality. You will work with the Drupal logging and mailing systems, learn how to output data using the theme layer and work with menus and links programmatically. Then, you will learn how to work with different kinds of data storages, create custom entities, field types and leverage the Database API for lower level database queries. You will further see how to introduce JavaScript into your module, work with the various file systems and ensure the code you write works on multilingual sites. Finally, you will learn how to programmatically work with Views, write automated tests for your functionality and also write secure code in general. By the end, you will have learned how to develop your own custom module that can provide complex business solutions. And who knows, maybe you’ll even contribute it back to the Drupal community. Foreword by Dries Buytaert, founder of Drupal.

Who is this book for?

The primary target of this book is Drupal developers who want to learn how to write modules and develop in Drupal 8. It is also intended for Drupal site builders and PHP developers who have basic Object Oriented Programming skills. A little bit of Symfony experience is helpful but not mandatory.

What you will learn

  • Develop Drupal 8 modules that do all the things you want
  • Master numerous Drupal 8 sub-systems and APIs in the process
  • Model, store, manipulate and process data to serve your purposes
  • Display data and content in a clean and secure way using the Drupal 8 theme system
  • Test your business logic to prevent regressions
  • Stay ahead of the curve and write code following the current best practices
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Table of Contents

19 Chapters
Developing for Drupal 8 Chevron down icon Chevron up icon
Creating Your First Module Chevron down icon Chevron up icon
Logging and Mailing Chevron down icon Chevron up icon
Theming Chevron down icon Chevron up icon
Menus and Menu Links Chevron down icon Chevron up icon
Data Modeling and Storage Chevron down icon Chevron up icon
Your Own Custom Entity and Plugin Types Chevron down icon Chevron up icon
The Database API Chevron down icon Chevron up icon
Custom Fields Chevron down icon Chevron up icon
Access Control Chevron down icon Chevron up icon
Caching Chevron down icon Chevron up icon
JavaScript and the Ajax API Chevron down icon Chevron up icon
Internationalization and Languages Chevron down icon Chevron up icon
Batches, Queues, and Cron Chevron down icon Chevron up icon
Views Chevron down icon Chevron up icon
Working with Files and Images Chevron down icon Chevron up icon
Automated Testing Chevron down icon Chevron up icon
Drupal 8 Security Chevron down icon Chevron up icon
Other Books You May Enjoy Chevron down icon Chevron up icon

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Amazon Customer Dec 31, 2020
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Really good book to get into the path or discovering the many secrets of Drupal 8 development
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Dmitrii Gladkov Apr 24, 2020
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Thanks to the authors of this book! Every aspect is explained in details. I strongly recommend this book as it is the best book for Drupal 8 module developers i've ever seen.
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Davide Inzerillo Aug 08, 2019
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delivery was made on the date indicated.The book has no signs of wear and is not ruined.Good book, the autor explain very well and is rich of example.
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Francesco Apr 23, 2022
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Acquistato il libro usato ad un prezzo eccellente e credo non sia mai stato aperto dal precedente proprietario
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Yelnats Oct 05, 2019
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It is how as expected.
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