Alter Drupal in Modules
Guide
Every web framework, including Drupal, has basically the same job: provide a way for developers to map URLs to the code that builds the corresponding pages. Drupal uses Symfony's HTTPKernel component. Kernel events are dispatched to coordinate the following tasks:
- Process the incoming request
- Figure out what to put on the page
- Create a response
- Deliver that response to the user's browser
Knowing a bit more about how Drupal handles the request-to-response workflow will help you better understand how to use routes and controllers to create your own custom pages or deal with authentication, access checking, and error handling in a Drupal module.
In this tutorial we'll:
- Walk through the process that Drupal uses to convert an incoming request into HTML that a browser can read
- See how the Symfony
HTTPKernelhelps orchestrate this process - Learn about how the output from a custom controller gets incorporated into the final page
By the end of this tutorial, you should be able to describe the process that Drupal goes through to convert an incoming request for a URL into an HTML response displayed by the browser.
One of the features of any content management system's architecture is the separation of presentation and data. In Drupal, modules are responsible for figuring out what should be on the page, and themes are responsible for the final look and feel of anything shown in the browser. It's vital for a module to return themeable output, so that the active theme can determine how it's presented.
In this tutorial, we'll:
- Define themeable output.
- Show how modules can avoid embedding presentation data in their output.
- Explain why Drupal favors structured arrays over HTML strings for data presentation.
By the end of this tutorial, you will be able to articulate the role modules play in enabling themes to customize a Drupal site's appearance.
Concept: Render API
FreeDrupal's Render API plays a crucial role in how content is presented on a site. The Render API manages how content is rendered through render arrays and render elements.
In this tutorial, we'll:
- Define render arrays, highlighting properties and elements.
- Explain how render elements are used as shorthand for complex structures.
- Describe the primary types of data we can use in a render array.
- Touch on the role of renderers and special methods for rendering entities.
By the end of this tutorial, you'll better understand how Drupal constructs a page's output through render arrays and streamlines rendering with render elements.
Props and slots are the two ways that data can be provided to a single directory component (SDC). They are part of a component's schema definition, and are used to determine the names of variables passed to a component's template file. Props pass structured, validated data into a component, while slots allow us to inject flexible content such as HTML or nested components. Understanding when and how to use each ensures you can build reusable and adaptable components.
In this tutorial, we'll:
- Learn what props and slots are, and how they differ.
- Discuss how using one or the other impacts the developer experience and use of your components in a UI.
- Practice deciding when to use each for component design.
By the end of this tutorial, you'll know how to choose between props and slots when building components.
Themes and modules can alter the list of theme hook suggestions in order to add new ones, remove existing ones, or reorder the list. This powerful feature allows for the definition of custom logic in your application that can tell Drupal to use different templates based on your own unique needs. You might for example; use a different page template for authenticated users, or a custom block template for someone's birthday.
In this tutorial we'll cover:
- Adding new theme hook suggestions from a theme using
hook_theme_suggestions_HOOK_alter() - Altering the list of theme hook suggestions
- Removing theme hook suggestions
- Reordering the list of theme hook suggestions
One of the primary ways that modules extend Drupal is by adding dynamic pages with content generated by application-specific logic. This tutorial looks at Drupal's process of handling a user's request and transforming it into a complete web page. We'll answer questions like:
- How does Drupal use Symfony's HttpKernel to process requests?
- How do user-configured blocks and the theme layer contribute to the page's content and appearance?
- What is the role of routes, controllers, and responses in this process?
In this tutorial, we'll:
- Follow the journey of a user request from URL to an HTML response in Drupal.
- Define the role of routes, controllers, and responses in Drupal's request handling.
- See how blocks and the theme layer contribute to the final output of a Drupal page.
By the end of this tutorial, you should be able to describe Drupal's request flow, understand the interaction of its key components in building a page, and appreciate the modular architecture that drives Drupal's flexibility.
Planning for a migration is essential. In our collective experience we've never once seen someone sit down and execute a migration flawlessly on their first attempt. Migrations involve preparing and analyzing your source data, building a new website that data can be migrated into, and lots of testing, rolling back, and testing again, in order to get everything right. By the end of this tutorial you should be ready to start planning for your own Drupal migration project, and have a better understanding of the challenges of migrating from one system to another.
Template files are used by modules when they need to add custom HTML to the content they output. The most common example is wrapping your output in one or more <div> tags to give it additional structure and context. Using custom template files in a Drupal module requires defining a new theme hook, creating the template file, an associating the appropriate data with the template file via a render array.
In this tutorial, we'll:
- Learn how to add a custom Twig template file to a module.
- Update the
WeatherPagecontroller to use the new template file.
By the end of this tutorial you should be able to create and use custom template files in a module.
The Views module is a query generator and render engine in Drupal core. It's typically used to create and output collections of items such as Drupal content entities. But it can also aggregate users, blocks, log records, and more. The output can be rendered many ways, including as a list, a grid, or an RSS feed. Views is commonly used in Drupal to create pages, blocks and other types of displays.
Through the Views API developers can expose new data to Views, add new configuration options, create new output plugins, field formatters, sort handlers, filter handlers, and more. By creating these customizations as extensions of Views instead of as stand alone queries, or hard-coded lists, you can empower site administrators to mix and match your customizations with the existing feature set in any way they might need.
In this tutorial we'll:
- Get a high level overview of the Views API.
- Discuss the functional parts of the Views API such as hooks, plugins, and data types.
- Learn how to use the Views API in your project.
By the end of this tutorial you'll have a solid understanding of the parts of the Views API and some guidance on which to use for your goals.
Before you begin a Drupal 6 or 7 (source) to Drupal 9 or 10 (destination) migration there are a number of things you should consider. Taking the time to plan your migration will help to ensure that you're successful. In this tutorial we'll take a high-level look at:
- Evaluating your existing Drupal 6/7 site for migration feasibility
- Preparing your source Drupal 6/7 site for a migration
- Preparing the destination Drupal site you're migrating to
By the end of this tutorial you should be ready to start assessing the feasibility of performing a successful migration, and begin making a migration plan.
This tutorial will help you understand the complete life cycle of a Drupal form: receiving the request from a browser, displaying a page with a form, rendering the form as HTML, handling the submitted form, validating input, handling errors, and processing data. We'll point out the common places that module developers might want to inject additional functionality into the process. And we'll link to tutorials with more details about each integration point in a form's life cycle.
In this tutorial, we'll:
- List the steps of the life cycle of a Drupal form.
- Describe how Drupal determines which form to display, and which form handles an HTTP POST request.
- Understand the role of
FormStateInterfacein the life cycle of a form.
By the end of this tutorial, you should have a solid understanding of the life cycle of a form within Drupal.
Previously, in Implement a Functional Test, we learned how to tell BrowserTestBase to use the Standard installation profile in order to get our test passing, letting the Standard profile implicitly provide our dependencies. We mentioned that doing so probably wasn't the best decision and that we should explicitly declare those dependencies instead.
In this tutorial, we'll walk through how to explicitly declare our test's dependencies. When in doubt, it's generally considered a best practice to be as explicit about the dependencies of our tests as possible. By the end of this tutorial, you should be able to:
- Understand why we want to explicitly declare our dependencies.
- Determine what the dependencies really are and make a list of them.
- Implement each dependency in our list.
- Emerge with a thorough passing test.
Drupal's Entity system provides several hooks that allow custom code to interact with various parts of the entity life cycle.
In this tutorial we'll:
- Examine the available hooks
- Learn how to make use of them to act on several different types of operations on individual entities
By the end if this tutorial you should have a better understanding of the hooks available to developers who want to respond to entity lifecycle operations and how to use them to customize the way specific entity types work.
The core structure of Drupal's Render API is the render array, which is a hierarchical associative array containing data to be rendered and properties describing how the data should be rendered. As a module developer you'll use render arrays to describe the content your module controls in order to output it on a page as HTML, or as part of a response in another format like JSON. As a theme developer, you'll manipulate render arrays in order to affect the way content is output on the page.
In this tutorial we'll learn:
- What render arrays are and why they exist
- The basic format of a render array
- What "properties" and "elements" signify in the context of a render array
- Where to find more information about how to create a render array to describe your own content
By the end of this tutorial you should be able to understand when you need to use a render array, recognize one when you see it, and know where to get more detailed information about render array formatting specifics.