CacheTagsInvalidator.php

<?php

namespace Drupal\Core\Cache;

use Drupal\Component\Assertion\Inspector;
use Symfony\Component\DependencyInjection\ContainerAwareTrait;

/**
 * Passes cache tag events to classes that wish to respond to them.
 */
class CacheTagsInvalidator implements CacheTagsInvalidatorInterface {
    use ContainerAwareTrait;
    
    /**
     * Holds an array of cache tags invalidators.
     *
     * @var \Drupal\Core\Cache\CacheTagsInvalidatorInterface[]
     */
    protected $invalidators = [];
    
    /**
     * {@inheritdoc}
     */
    public function invalidateTags(array $tags) {
        assert(Inspector::assertAllStrings($tags), 'Cache tags must be strings.');
        // Notify all added cache tags invalidators.
        foreach ($this->invalidators as $invalidator) {
            $invalidator->invalidateTags($tags);
        }
        // Additionally, notify each cache bin if it implements the service.
        foreach ($this->getInvalidatorCacheBins() as $bin) {
            $bin->invalidateTags($tags);
        }
    }
    
    /**
     * Reset statically cached tags in all cache tag checksum services.
     *
     * This is only used by tests.
     */
    public function resetChecksums() {
        foreach ($this->invalidators as $invalidator) {
            if ($invalidator instanceof CacheTagsChecksumInterface) {
                $invalidator->reset();
            }
        }
    }
    
    /**
     * Adds a cache tags invalidator.
     *
     * @param \Drupal\Core\Cache\CacheTagsInvalidatorInterface $invalidator
     *   A cache invalidator.
     */
    public function addInvalidator(CacheTagsInvalidatorInterface $invalidator) {
        $this->invalidators[] = $invalidator;
    }
    
    /**
     * Returns all cache bins that need to be notified about invalidations.
     *
     * @return \Drupal\Core\Cache\CacheTagsInvalidatorInterface[]
     *   An array of cache backend objects that implement the invalidator
     *   interface, keyed by their cache bin.
     */
    protected function getInvalidatorCacheBins() {
        $bins = [];
        foreach ($this->container
            ->getParameter('cache_bins') as $service_id => $bin) {
            $service = $this->container
                ->get($service_id);
            if ($service instanceof CacheTagsInvalidatorInterface) {
                $bins[$bin] = $service;
            }
        }
        return $bins;
    }

}