A Drupal 8 block plugin which needs to be shown only on node pages (using route matcher)

TextAdsBlock.php

<?php

namespace Drupal\my_module\Plugin\Block;

use Drupal\Core\Access\AccessResult;
use Drupal\Core\Block\BlockBase;
use Drupal\Core\Cache\Cache;
use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\Session\AccountInterface;
use Drupal\node\NodeInterface;
use Drupal\my_lists\ProfilesService;
use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * Provides a 'TextAdsBlock' block.
 *
 * @Block(
 *   id = "text_ads",
 *   admin_label = @Translation("Text Ads"),
 *   category = @Translation("Ads")
 * )
 */
class TextAdsBlock extends BlockBase implements ContainerFactoryPluginInterface {

  /**
   * Drupal\my_lists\ProfilesService definition.
   *
   * @var \Drupal\my_lists\ProfilesService
   */
  protected $profilesService;

  protected $routeMatch;

  protected function getNode() {
    $obj = $this->routeMatch->getParameter('node');
    if (!$obj instanceof NodeInterface) {
      throw new \UnexpectedValueException("Not a node page");
    }

    if ($obj->bundle() !== 'article') {
      throw new \UnexpectedValueException("Not an article node");
    }

    return $obj;
  }

  protected function blockAccess(AccountInterface $account) {
    try {
      $node = $this->getNode();
    }
    catch (\UnexpectedValueException $ex) {
      return AccessResult::forbidden();
    }

    return parent::blockAccess($account);
  }

  public function __construct(
    array $configuration,
    $plugin_id,
    $plugin_definition,
    ProfilesService $profiles_service,
    RouteMatchInterface $route_match
  ) {
    parent::__construct($configuration, $plugin_id, $plugin_definition);
    $this->profilesService = $profiles_service;
    $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('my_lists.profiles'),
      $container->get('current_route_match')
    );
  }

  /**
   * {@inheritdoc}
   */
  public function build() {
    // TODO: Filter the profiles based on current node type and location.
    $profiles = array_slice($this->profilesService->getProfiles(), 0, 15);

    $build = [
      '#theme' => 'my_text_ads',
      '#profiles' => $profiles,
    ];

    return $build;
  }

  public function getCacheTags() {
    $node = $this->getNode();
    return Cache::mergeTags(parent::getCacheTags(), ['node:' . $node->id()]);
  }

  public function getCacheContexts() {
    return Cache::mergeContexts(parent::getCacheContexts(), ['route']);
  }

}