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Drupal is a good CMS, that anyone with some development experience, can use to develop websites and applications. In today’s article we are going to continue with our series on Drupal 8, the best CMS in the whole wide world and focus on Views.
The Views feature that is included with Drupal, allow a user to create a list of content to present on their website. The display of views is handled by the core Views module, and users can create and edit their views through the Views UI.
Any content that is stored on a website’s database can be displayed using Views, in different ways, such as table with sortable fields, grid layouts, teasers or pictures that link to articles, blocks, JSON output, RSS feeds, calendar and on-screen slideshows. A view has several parts, which can be seen by a user when he/she is creating a view, such parts are the display (page, block, feed, attachment), format, fields, filter criteria, sort criteria, contextual filters and relationships.
Views essentially allows users to create a list of content, for a website, without having to know any SQL or know the database. Views allow users to choose, the format of the results, users can open the format windows, and choose a format from the list of formats. Such formats are the grid, an HTLM list, Jump menu, a table and an unformatted list.
A user can add fields to the view, to show, the contents of its database, the fields can be chosen only when a user chooses a certain format, such as an HTML list. As the user ads fields to his/her views configuration, it is important to note that as the user ads these fields, he/she is presented with a dialog box, that prompts them to set certain settings options for a field.
Users can also choose where their views are going to appear on the page, when they turn their views into a block and choose where to place the block, in the block layout page. Users can also choose to rewrite the results of their views, by changing the settings options, under the rewrite results tab. Views formatter allow users to change the way, in which views display information to users on a website.
The style of a view can also be manipulated, by going into the settings options for each field, under the style settings tab of the settings. Users can choose their HTML element, add a CSS class, wrap the field’s label, and create a class for that field as well. If a user wants to limit the amount of CSS classes that Drupal adds by default, the user can uncheck the add default classes box found under the fields’ settings under style settings.
The views module allows users to use the power of relationships, for them to relate tables together and pull information from both tables. Developers can relate two tables, by adding a relationship, under the advance settings options, under add a relationship. Once the relationship has been added, then the user can add the field from the other tables, which have been related to the view. Users also have the option to put two table columns together, in the table’s setting under format, when users chose the table format option.
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\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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