--- /dev/null
+<?php
+
+namespace Drupal\{{ machine_name }}\Plugin\views\argument_default;
+
+use Drupal\Core\Cache\Cache;
+use Drupal\Core\Cache\CacheableDependencyInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\views\Plugin\views\argument_default\ArgumentDefaultPluginBase;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Example of argument default plugin.
+ *
+ * @ViewsArgumentDefault(
+ * id = "{{ plugin_id }}",
+ * title = @Translation("{{ plugin_label }}")
+ * )
+ */
+class {{ class }} extends ArgumentDefaultPluginBase implements CacheableDependencyInterface {
+
+ /**
+ * The route match.
+ *
+ * @var \Drupal\Core\Routing\RouteMatchInterface
+ */
+ protected $routeMatch;
+
+ /**
+ * Constructs a new {{ class }} instance.
+ *
+ * @param array $configuration
+ * A configuration array containing information about the plugin instance.
+ * @param string $plugin_id
+ * The plugin_id for the plugin instance.
+ * @param mixed $plugin_definition
+ * The plugin implementation definition.
+ * @param \Drupal\Core\Routing\RouteMatchInterface $route_match
+ * The route match.
+ */
+ public function __construct(array $configuration, $plugin_id, $plugin_definition, RouteMatchInterface $route_match) {
+ parent::__construct($configuration, $plugin_id, $plugin_definition);
+
+ // @DCG
+ // The Route match service is used to extract argument from the current
+ // route.
+ $this->routeMatch = $route_match;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+ return new static(
+ $configuration,
+ $plugin_id,
+ $plugin_definition,
+ $container->get('current_route_match')
+ );
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ protected function defineOptions() {
+ $options = parent::defineOptions();
+ $options['example_option'] = ['default' => ''];
+ return $options;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function buildOptionsForm(&$form, FormStateInterface $form_state) {
+ $form['example_option'] = [
+ '#type' => 'textfield',
+ '#title' => t('Some example option'),
+ '#default_value' => $this->options['example_option'],
+ ];
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function getArgument() {
+
+ // @DCG
+ // Here is the place where you should create a default argument for the
+ // contextual filter. The source of this argument depends on your needs.
+ // For example, you can extract the value from the URL or fetch it from
+ // some fields of the current viewed entity.
+ // For now let's use example option as an argument.
+ $argument = $this->options['example_option'];
+
+ return $argument;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function getCacheMaxAge() {
+ return Cache::PERMANENT;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function getCacheContexts() {
+ return ['url'];
+ }
+
+}