As fantastic as these features are, they will certainly not satisfy the needs of all users. To that end, Drupal's capabilities can be easily extended with modules, themes, and installation profiles. Take a look at Drupal's main website, (http://drupal.org), and you will find thousands of modules that provide new features and thousands of themes that transform the look and feel of the application or website.
The flexible way Drupal can be extended and transformed through the module and theme mechanisms has led many to claim that Drupal isn't just a CMS, but a Content Management Framework (CMF) capable of being re-tooled to specific needs and functional requirements. This is particularly the case with Drupal 8—the latest version of Drupal and the focus of this book—as great progress has been made on the extensibility front as well.
Establishing whether Drupal is rightly called a CMS or CMF is beyond our purpose here, but it is certain that Drupal's most tremendous asset is its extensibility. Want to use a directory server for authentication? There's a Drupal module for that. Want to export data to Comma-separated Version (CSV) files? There are several modules for that (depending on what data you want to export). Interested in Facebook support, integration with Twitter, or adding a Share This button? Yup, there are modules for those too—all of which are available on Drupal.org and provided by developers like you.
Want to integrate Drupal with that custom tool you wrote to solve your special business needs? There may not be a module for that, but with a little bit of code, you can write your own. In fact, that is the subject of this book—providing you with the knowledge and tools to achieve your own goals.
In summary, the purpose of this book is to get you ramped up (as quickly as possible) for Drupal 8 module development. As we move chapter by chapter, we will cover the APIs and tools that you will use to build custom Drupal sites, and we won't stick to theory. Most chapters provide working, practically-oriented example code designed to show you how to implement the concepts we will be talking about. We will follow Drupal coding conventions and utilize Drupal design patterns in an effort to illustrate the correct way to write code within the Drupal development context.
While I certainly can't write the exact code to meet your needs, my hope is that the code mentioned in these chapters can serve as a foundation for your bigger and better applications.
So let's get started with a few preliminary matters to better understand Drupal.