CacheFactory.php

<?php

namespace Drupal\Core\Cache;


/**
 * Defines the cache backend factory.
 */
use Drupal\Core\Site\Settings;
use Symfony\Component\DependencyInjection\ContainerAwareInterface;
use Symfony\Component\DependencyInjection\ContainerAwareTrait;
class CacheFactory implements CacheFactoryInterface, ContainerAwareInterface {
    use ContainerAwareTrait;
    
    /**
     * The site settings.
     *
     * @var \Drupal\Core\Site\Settings
     */
    protected $settings;
    
    /**
     * A map of cache bin to default cache backend service name.
     *
     * All mappings in $settings takes precedence over this, but this can be used
     * to optimize cache storage for a Drupal installation without cache
     * customizations in settings.php. For example, this can be used to map the
     * 'bootstrap' bin to 'cache.backend.chainedfast', while allowing other bins
     * to fall back to the global default of 'cache.backend.database'.
     *
     * @var array
     */
    protected $defaultBinBackends;
    
    /**
     * Constructs CacheFactory object.
     *
     * @param \Drupal\Core\Site\Settings $settings
     *   The site settings.
     * @param array $default_bin_backends
     *   (optional) A mapping of bin to backend service name. Mappings in
     *   $settings take precedence over this.
     */
    public function __construct(Settings $settings, array $default_bin_backends = []) {
        $this->settings = $settings;
        $this->defaultBinBackends = $default_bin_backends;
    }
    
    /**
     * Instantiates a cache backend class for a given cache bin.
     *
     * By default, this returns an instance of the
     * Drupal\Core\Cache\DatabaseBackend class.
     *
     * Classes implementing Drupal\Core\Cache\CacheBackendInterface can register
     * themselves both as a default implementation and for specific bins.
     *
     * @param string $bin
     *   The cache bin for which a cache backend object should be returned.
     *
     * @return \Drupal\Core\Cache\CacheBackendInterface
     *   The cache backend object associated with the specified bin.
     */
    public function get($bin) {
        $cache_settings = $this->settings
            ->get('cache');
        // First, look for a cache bin specific setting.
        if (isset($cache_settings['bins'][$bin])) {
            $service_name = $cache_settings['bins'][$bin];
        }
        elseif (isset($this->defaultBinBackends[$bin])) {
            $service_name = $this->defaultBinBackends[$bin];
        }
        elseif (isset($cache_settings['default'])) {
            $service_name = $cache_settings['default'];
        }
        else {
            // Fall back to the database backend if nothing else is configured.
            $service_name = 'cache.backend.database';
        }
        return $this->container
            ->get($service_name)
            ->get($bin);
    }

}