Preprocess functions allow Drupal themes to manipulate the variables that are used in Twig template files by using PHP functions to preprocess data before it is exposed to each template. All of the dynamic content available to theme developers within a Twig template file is exposed through a preprocess function. Understanding how preprocess functions work, and the role they play, is important for both module developers and theme developers.
In this tutorial we'll learn:
- What preprocess functions are and how they work
- The use case for preprocess functions
- The order of execution for preprocess functions
By the end of this tutorial you should be able to explain what preprocess functions are and the role they play in a Drupal theme.
Template files are responsible for the HTML markup of every page generated by Drupal. Any file ending with the .html.twig extension is a template file. These files are composed of standard HTML markup as well as tokens used by the Twig template engine to represent dynamic content that will be substituted into the HTML markup when the template is used. As a theme developer, you'll work with this a lot.
In this tutorial we’re going to learn about:
- What template files are, and how they fit into the big picture of creating a theme
- How template files are used in order to allow theme developers to modify the HTML markup output by Drupal
- Naming conventions for, and specificity of, template files
What Is a Theme?
FreeThemes are the part of Drupal that you, and anyone else visiting your Drupal powered application, see when they view any page in their browser. You can think of a theme as a layer, kind of like a screen, that exists between your Drupal content and the users of your site. Whenever a page is requested Drupal does the work of assembling the content to display into structured data which is then handed off to the presentation layer to determine how to visually represent the data provided.
Drupal themes are created by front-end developer. Frequently referred to as themers, or theme developers. Themes consist of standard web assets like CSS, JavaScript, and images, combined with Drupal-specific templates for generating HTML markup, and YAML files for telling Drupal about the file and features that make up each individual theme.
In this tutorial we'll:
- Explain what a Drupal theme is.
- Explain the role of a Drupal themer in the process of building a Drupal site.
- Get a high level overview of the types of files/code that themes are made of.
By the end of this tutorial you should be able to explain what a Drupal theme is, and the kind of work a Drupal theme developer will be expected to do.
Maybe you've heard of anonymous closures but you're not quite sure how they apply in Drupal, or why using them is considered a best-practice. Anonymous closures allow you to avoid accidentally clashing with anything in the global scope, as well as to alias the jQuery object to the more commonly used $
. This is necessary because Drupal runs jQuery in no-conflict mode. This tutorial will look at the syntax used for placing your custom JavaScript code inside an anonymous closure, and why it's a good idea to do so.
In this tutorial we'll:
- Explain what a closure is (briefly), and what immediately invoked function expressions are
- Show how typically Drupal JavaScript gets wrapped in a closure
- Provide a copy/paste example you can use in your own code
By the end of this tutorial you should be able to explain what an anonymous closure is, and how to use one in your custom JavaScript for Drupal.
Drupal Console
FreeThe Drupal Console is a suite of tools run from a command line interface (CLI) to generate boilerplate code and interact with a Drupal installation.
Note: This project is no longer actively maintained. See the Drush topic for alternative solutions.
Like most output in Drupal, Views relies on Twig templates for a significant amount of its rendering. In this tutorial we'll identify where you can find the default Views templates within your file system, what the common templates are for, and how to name your templates so that they are applied to specific views.
By the end of this tutorial, you should be able to:
- Identify where to find default views templates
- Understand which templates apply to what part of a view
- Get a sense of the template suggestions and how to use them to limit where your custom templates are applied
- Identify a view's machine name
- Identify a display's machine name
- Identify a field's machine name
Now that we understand what templates are and how we can use them, let's override some templates! In this tutorial we'll copy the views wrapper template to our theme and override it so that we can customize the markup for the Baseball Players view. Then we'll modify the template so that our view's pager appears both above and below our table of players.
To follow along with our Drupal Views tutorials, set up a Drupal site loaded with our 4 custom views and baseball stats content that will make querying in Views a bit more interesting and meaningful.
By the end of this tutorial, you should choose a solution and follow the instructions for creating a Drupal site loaded with our starting point content and views.
Often, there's an existing Drush command that does most of what you want, but needs just a few tweaks or enhancements to make it meet your project requirements. Maybe the existing core Drush command has the functionality but lacks some additional validation. Or maybe you need to add an additional option to perform some application-specific debugging logic for all commands in a group.
Drush hooks can be used to alter, extend, and enhance existing Drush commands.
In this tutorial we'll:
- Learn how to alter a Drush command with code in a custom module
- Declare a validation hook that alters the
user:password
command with additional password validation logic
By the end of this tutorial you should be able to alter a Drush command provided by Drush core or a contributed module with your own custom code.
Back-end developers, and Drupal site builders, often find themselves having to perform the same UI steps over and over again, like exporting configuration, importing configuration changes, running cron, processing a large queue of jobs, indexing items for Search API, and more. Performing these tasks with Drush saves time and reduces the number of clicks required.
Drush core contains commands to execute all the most common tasks. Many contributed modules provide their own Drush commands to make interaction with the module's features, easier, faster, and scriptable.
In this tutorial we'll:
- Learn about the Drush core commands for common tasks like interacting with queues, performing database backups, and importing/exporting configuration
- Demonstrate how to find the Drush commands provided by contributed modules in your project
By the end of this tutorial you'll learn some popular commands for common tasks that'll speed up your daily work.
Every Drupal site consists of many Drupal projects like modules and themes. Drush comes with a group of commands that aid in managing projects from the command line. These commands can check which modules are present in a site's codebase, report their security status, enable modules, and display metadata for modules and themes. All of these commands start with the pm
prefix, and are part of the project manager group.
Common use cases for the project manager commands include: quickly enabling/disabling modules via the CLI rather than performing numerous clicks in the UI, and as part of CI/CD process that lists (or maybe even automates) security updates.
In this tutorial we'll:
- List the available
pm
commands - Enable a module with Drush
- Uninstall a module with Drush
- Use Drush to check for security updates for modules, themes and PHP packages
By the end of this tutorial you'll have an understanding of the project manager commands that come with Drush, how to use them, and how to speed up common workflows and maintenance tasks.
Administration and maintenance of Drupal websites consists of many tasks that can both be performed via the command line, and automated, with Drush. Using Drush's site and environment administration commands you can run database updates, check an environment's status, clear (rebuild) the cache, perform Cron-related operations, and manage users. These tasks are repetitive, often require many steps in the UI, and may be tedious in the long run. Learning to execute them with Drush can save you time and allows for more automation of common tasks.
In this tutorial we'll:
- Use Drush to check a site's status
- Learn how to perform database updates with Drush
- Clear the Drupal cache with Drush
- Use Drush to execute Cron tasks for a Drupal site
- Learn how to use Drush to login to a site as any user, and manage existing users
By the end of this tutorial you'll be able to perform many common Drupal environment and administration tasks from the command line with Drush. We're not going to cover all of the environment management commands in this tutorial, just some of the more popular ones. We encourage you to explore further on your own.
What Is Drush?
FreeDrush, aka The Drupal Shell, is a command line utility and UNIX scripting interface for Drupal. It allows access to common Drupal features and tasks via the command line. It can help speed up common tasks for Drupal site builders, developers, and DevOps teams. Among other things, it makes it easier to integrate Drupal into CI/CD workflows.
In this tutorial we'll:
- Learn what Drush is and what can be done with Drush
- Install Drush
- Find a list of Drush commands
- Learn how to execute commands
By the end of this tutorial, you'll understand how to install and use Drush with your Drupal projects, navigate the list of its commands and run them. This is intended as an overview. Other tutorials will provide more detail about common commands and use-cases.
Make your custom Drush command more flexible by allowing users to pass command line arguments into it. For example, rather than hard-coding that the command lists users with a specific status, allow the desired status to be specified at run-time. This allows the command's logic to be more generic, and to return different results, or operate on different data, based on the provided parameters.
Parameters are variables that are passed from user input at the command line into the Drush command method. Typically, they are either single string values, or comma-delimited strings of values. Parameters are typically used to provide input for the command related to what the command should work on, in contrast to options, which are typically used to configure how the command works.
In this tutorial we'll:
- Declare parameters for a custom Drush command in its annotation
- Use the parameter input inside the custom Drush command method
By the end of this tutorial you should understand how to work with parameters inside custom Drush commands.
When you create a custom Drush command it might be useful to allow users to pass options (predefined values) that change the way a command works. You can think of options as being flags, or variables, that affect the command's internal logic. As an example, consider the Drush core user:login
command which by default returns a one-time login link for the root account. The command also accepts an optional --name
option which allows the internal logic to create a link for a specified user instead of only being able to create links for the root user. This makes the command useful in a wider variety of situations. Another common option is the --format
option which allows a user to specify that they want the command to return its output in a format (CSV, JSON, Table, etc.) other than the default.
Options are defined in the Drush command's annotation. Their values are passed as part of an associative array to the command method. Unlike parameters, options are not ordered, so you can specify them in any order, and they are called with two dashes like --my-option
. Options are always optional, not required, and can be set up to accept a value --name=John
or as a boolean flag without a value --translate
.
In this tutorial we'll:
- Declare options for a custom Drush command in its annotation
- Learn how to use these options inside the custom Drush command method
By the end of this tutorial you should be able to add options to your own custom Drush commands.
Drush commands are commonly run in the Drupal docroot, the directory where Drupal's files live. This is a relatively simple task on your local development environment. But if you're working on multiple sites and each of those sites has one or more remote environments that you connect to via SSH, workflows quickly become complicated. Creating and using Drush site aliases allows you to run Drush commands on any site, local or remote, that you have credentials to access, from any location on your computer that has access to a Drush executable.
Imagine you've got a Drupal project with dev, test, and live environments in the cloud somewhere. And you need to clear the cache on the dev environment. You could SSH to that environment, and execute drush cr
there. Or, after configuring a site alias you could do something like:
drush @provider.dev cr -y
And Drush will connect to the remote environment and clear the cache.
Site aliases allow bundling the configuration options (--uri
, --root
, etc.) for a specific remote server under an alias. This reduces the amount of typing required. Even more importantly, it helps teams agree on a common definition for environments like @dev
, @test
, and @live
by committing their configurations to version control.
In this tutorial we'll:
- Define what a Drush site alias is
- Understand the use case for aliases
- Learn how to configure and use Drush site aliases
By the end of this tutorial, you should understand how Drush site aliases work, how to create Drush site aliases, and how to use them in a Drush command.
The Drush executable can be configured through the use of YAML configuration files and environment variables. This configuration can help cut down on typing lengthy frequently-used commands. You can tell Drush to look for command files in project-specific locations. Configuration can also set the value(s) of a specific command's options, instead of having to type them at the command line every time.
In this tutorial we'll:
- Explore different Drush configuration options
- Learn how to configure Drush for your project
By the end of this tutorial, you'll know how to provide project specific, and global, configuration that helps customize Drush and improve your own efficiency.
Creating a custom Drush command requires creating a PHP class that Drush can find with annotated methods and metadata about each custom command. You'll create a drush.services.yml file that tells Drush where to find the command class and any services to inject into it. You'll also modify the project's composer.json to tell Drush what versions of Drush the command is compatible with.
Custom Drush commands are a great way to expose your custom module's features to help automate these tasks and allow users to perform them as background processes. They can also provide a more efficient way to execute PHP code that takes a long time and is prone to timing out when run via the web server.
Depending on your use-case it can also be more efficient to create a custom Drush command to execute your logic instead of coding a complete UI. For example, if all the command needs to do is generate a CSV list it might take less effort to write a Drush command and pipe the output to a file than to create a UI that generates a file and prompts the user to download it.
In this tutorial we'll:
- Declare a new custom Drush command inside a custom module
- Make our custom Drush command output a list of all the blocked users on the site
- Verify our new command is working
By the end of this tutorial you should understand how to create a custom Drush command that returns a list of blocked users.
Developers can implement the Drush command API to write their own custom Drush commands. This allows you to include Drush commands with your modules to allow the module's features to be used via the CLI. You can also create project-specific Drush commands that help with the development, deployment, and maintenance of your particular application.
We've written Drush commands to help generate reports, make it easier for new team members to get up and running, compile custom theme assets, and more. Any time we need to write PHP code that interacts with our Drupal site where we're worried the code might time out because it takes too long to execute we'll reach for Drush. Custom Drush commands are also useful to combine background processes that can be executed on cron, such as nightly imports, data synchronization, bulk database manipulation, custom queues processing, and so much more.
In this tutorial we'll:
- Learn about different types of custom Drush commands
- Review the anatomy of a Drush command
- See how the Drush bootstrap process relates to commands
By the end of this tutorial, you'll be able to identify the parts of a custom Drush command and start writing your own.
In addition to using one of the existing generators, developers can write their own Drush generator commands. This can help speed up repetitive tasks and reduce the use of boilerplate code that is prone to human error.
Generators are provided through Drush's integration with the Drupal Code Generator project. Writing new generators isn't specific to Drush, though if you're creating generators for Drupal it is definitely easiest with Drush as a wrapper.
Similar to Drush commands, generators can be supplied by a Drupal module or declared globally. If you have a feature-specific functionality, it's best to ship your custom generator within the custom module. Otherwise, a global generator can be declared and used.
In this tutorial we'll:
- Explain the anatomy of a Drush generator
- Write a custom Drush generator for handling a site's development.services.yml file, and use it in a project
By the end of this tutorial you should understand how to create, or customize, a Drush code generator and use it in your project.