BlockManager.php

<?php

/**
 * Contains \Drupal\block\Plugin\Type\BlockManager.
 */
namespace Drupal\block\Plugin\Type;

use Drupal\Component\Plugin\PluginManagerBase;
use Drupal\Component\Plugin\Discovery\DerivativeDiscoveryDecorator;
use Drupal\Core\Cache\CacheBackendInterface;
use Drupal\Core\Language\Language;
use Drupal\Core\Plugin\Discovery\AnnotatedClassDiscovery;
use Drupal\Core\Plugin\Discovery\AlterDecorator;
use Drupal\Core\Plugin\Discovery\CacheDecorator;
use Drupal\Component\Plugin\Factory\DefaultFactory;

/**
 * Manages discovery and instantiation of block plugins.
 *
 * @todo Add documentation to this class.
 *
 * @see \Drupal\block\BlockPluginInterface
 */
class BlockManager extends PluginManagerBase {

  /**
   * Constructs a new \Drupal\block\Plugin\Type\BlockManager object.
   *
   * @param \Traversable $namespaces
   *   An object that implements \Traversable which contains the root paths
   *   keyed by the corresponding namespace to look for plugin implementations,
   */
  public function __construct(\Traversable $namespaces) {
    $this->discovery = new AnnotatedClassDiscovery('Block', $namespaces);
    $this->discovery = new DerivativeDiscoveryDecorator($this->discovery);
    $this->discovery = new AlterDecorator($this->discovery, 'block');
    $this->discovery = new CacheDecorator($this->discovery, 'block_plugins:' . language(Language::TYPE_INTERFACE)->langcode, 'block', CacheBackendInterface::CACHE_PERMANENT, array(
      'block',
    ));
    $this->factory = new DefaultFactory($this->discovery);
  }

}