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In today’s article, we are going to continue our conversation on Drupal 8 about Entities, which is a fundamental concept in Drupal 8, because entities are found in nearly every component that make up Drupal 8. In your application, if you’d like to encapsulate the behavior of specific data structures, you can create your own entity types, and by altering existing ones, you can make them work more efficiently.
The basic building blocks of Drupal’s data model, are known as entities, because they make up the visible content, which a user has to interact with, when he/she visit a website. The two types of entities are configuration entities and content entities; it is important to understand the basic difference between these types of entities.
Configurable settings on a Drupal site, can be stored inside an object known as configuration entities. The core’s configuration management system, allow developers to export configuration entities. Default configurations, which can be set during Drupal’s installation or when a new module is enabled can be set, by configuration entities. The code that is in a module would generally limit the data structure of a configuration entity.
The next type of entity allows additional fields to be attached to it, they are configurable, and they support translation and revisions, this type of entity is known as content entities. Users, blocks, taxonomy terms and nodes are all included in Drupal’s core installation as content entities.
The entity API in Drupal is very complex, if we don’t understand key terms such as entities; there are other key terms to keep in mind as well. Another key term in Drupal’s entity API is bundles, which are container for a sub-group of an entity. The article, basic page, blog post, etc., are all bundles of the node entity type; and individual vocabularies of a taxonomy entity type, would have their own bundles.
Another buzz word in the Drupal entity API world is fields, which make up the details of the data model, through individual or compound data elements. Boolean, decimal, float, integer, entity reference, link, image, email, telephone, and several text fields are all the fields offered by Drupal.
Bundles of the same entity types, will contain fields that have different variation of configurations among them. Plugins is also part of the entity API, and it is also another term that we need to learn if we want to encapsulate re-usable behaviors. We will talk more in depth about plugins in future article posts, just know that plugins are a general reusable solution, to recurring problems.
Another Drupal entity API buzz word is annotations, which are used throughout Drupal core, and it is another Drupal concept you should know, as a Drupal developer. Annotations are especial formatted PHP code comments which are parsed to provide class discovery and metadata description to Drupal.
Storage, access control, building lists and views of entities, and the forms required for creating, viewing, updating and deleting entities is all managed by handlers, which is another Drupal entity api term that need to be known by any Drupal developer.
Thank you for reading this article!!!
\Drupal\Component\Plugin\PluginManagerInterface,Implements all plugin managers, and this piece of code extends these three pieces of code, which are the basis for any new plugin manager.
\Drupal\Component\Plugin\Discovery\DiscoveryInterface, \Drupal\Component\Plugin\Factory\FactoryInterface and, \Drupal\Component\Plugin\Mapper\MapperInterface.The plugin.manager.* a piece of code is used to generate plugin manager services and from the service container, a copy of the plugin manager can be requested. Example:
$example_manager = \Drupal::service('plugin.manager.example');Once a developer has identified the plugin manager needed, to complete a task, then that developer has to start, by locating the name of the plugin manager service he/she needs. The controller will be the place where, a developer can inject their plugin manager services, and this is the Drupal way of doing things. The code below is a controller file, located under custom_module/src/Controller, it is very important that you get those names and file directory correct, for Drupal to recognize your controller and plugin.
<?php namespace Drupal\plugin_type_example\Controller; use Drupal\Core\Controller\ControllerBase; use Drupal\plugin_type_example\SandwichPluginManager; use Symfony\Component\DependencyInjection\ContainerInterface; /** * Controller for our example pages. */ class PluginTypeExampleController extends ControllerBase { /** * The sandwich plugin manager. * * We use this to get all of the sandwich plugins. * * @var \Drupal\plugin_type_example\SandwichPluginManager */ protected $sandwichManager; /** * Constructor. * * @param \Drupal\plugin_type_example\SandwichPluginManager $sandwich_manager * The sandwich plugin manager service. We're injecting this service so that * we can use it to access the sandwich plugins. */ public function __construct(SandwichPluginManager $sandwich_manager) { $this->sandwichManager = $sandwich_manager; } /** * {@inheritdoc} * * Override the parent method so that we can inject our sandwich plugin * manager service into the controller. * * For more about how dependency injection works read https://www.drupal.org/node/2133171 */ public static function create(ContainerInterface $container) { // Inject the plugin.manager.sandwich service that represents our plugin // manager as defined in the plugin_type_example.services.yml file. return new static($container->get('plugin.manager.sandwich')); } }All defined plugins have information that can aid our application development to move forward faster. All that information from defined plugins is available to developers when they can make calls to the getDefinitions method. Enabled modules, can be used to locate all plugin definitions of the type in question, through the discovery handler . When the discovery handler is not used to retrieve data, then the DefaultPluginManager is used to retrieve the data from the cache if the data is available there. A good example of is in the code below, watch how the definitions of a plugin can be obtained in the code.
// Get the list of all the sandwich plugins defined on the system from the // plugin manager. Note that at this point, what we have is *definitions* of // plugins, not the plugins themselves. $sandwich_plugin_definitions = $this->sandwichManager->getDefinitions(); // Let's output a list of the plugin definitions we now have. $items = array(); foreach ($sandwich_plugin_definitions as $sandwich_plugin_definition) { // Here we use various properties from the plugin definition. These values // are defined in the annotation at the top of the plugin class: see // \Drupal\plugin_type_example\Plugin\Sandwich\ExampleHamSandwich. $items[] = t("@id (calories: @calories, description: @description )", array( '@id' => $sandwich_plugin_definition['id'], '@calories' => $sandwich_plugin_definition['calories'], '@description' => $sandwich_plugin_definition['description'], )); } // Add our list to the render array. $build['plugin_definitions'] = array( '#theme' => 'item_list', '#title' => 'Sandwich plugin definitions', '#items' => $items, );When a list of plugin types is desired by a developer he/she may want to use the method above to accomplish this task. The unique ID of a plugin can be utilized in order to retrieve the definition of the plugin in question, calling the getDefinition($plugin_id) method. // If we want just a single plugin definition, we can use getDefinition(). // This requires us to know the ID of the plugin we want. This is set in the // annotation on the plugin class: see \Drupal\plugin_type_example\Plugin\Sandwich\ExampleHamSandwich. $ham_sandwich_plugin_definition = $this->sandwichManager->getDefinition('meatball_sandwich'); In order to instantiate and use an individual plugin object, the createInstance($plugin_id) method can be used. It is not good practice to instantiate a plugin object directly, instead, the plugin manager should be used to do so. Understanding how instances of a plugin are created requires that you see it in action, in the code below.
// To get an instance of a plugin, we call createInstance() on the plugin // manager, passing the ID of the plugin we want to load. Let's output a // list of the plugins by loading an instance of each plugin definition and // collecting the description from each. $items = array(); // The array of plugin definitions is keyed by plugin id, so we can just use // that to load our plugin instances. $sandwich_plugin_definitions = $this->sandwichManager->getDefinitions(); foreach ($sandwich_plugin_definitions as $plugin_id => $sandwich_plugin_definition) { // We now have a plugin instance. From here on it can be treated just as // any other object; have its properties examined, methods called, etc. $plugin = $this->sandwichManager->createInstance($plugin_id); $items[] = $plugin->description(); }All the code on this tutorial was taken from Drupalize.me. Thank you for reading this article!!!
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