MissingContentEvent example

protected function processMissingContent(&$context) {
    $sandbox = &$context['sandbox']['config'];
    if (!isset($sandbox['missing_content'])) {
      $missing_content = $this->configManager->findMissingContentDependencies();
      $sandbox['missing_content']['data'] = $missing_content;
      $sandbox['missing_content']['total'] = count($missing_content);
    }
    else {
      $missing_content = $sandbox['missing_content']['data'];
    }
    if (!empty($missing_content)) {
      $event = new MissingContentEvent($missing_content);
      // Fire an event to allow listeners to create the missing content.       $this->eventDispatcher->dispatch($event, ConfigEvents::IMPORT_MISSING_CONTENT);
      $sandbox['missing_content']['data'] = $event->getMissingContent();
    }
    $current_count = count($sandbox['missing_content']['data']);
    if ($current_count) {
      $context['message'] = $this->t('Resolving missing content');
      $context['finished'] = ($sandbox['missing_content']['total'] - $current_count) / $sandbox['missing_content']['total'];
    }
    else {
      $context['finished'] = 1;
    }