setDeleted example

public function onFieldStorageDefinitionDelete(FieldStorageDefinitionInterface $storage_definition) {
    $entity_type_id = $storage_definition->getTargetEntityTypeId();

    // @todo Forward this to all interested handlers, not only storage, once     // iterating handlers is possible: https://www.drupal.org/node/2332857.     $storage = $this->entityTypeManager->getStorage($entity_type_id);

    // Keep the field definition in the deleted fields repository so we can use     // it later during field_purge_batch(), but only if the field has data.     if ($storage_definition instanceof BaseFieldDefinition && $storage instanceof FieldableEntityStorageInterface && $storage->countFieldData($storage_definition, TRUE)) {
      $deleted_storage_definition = clone $storage_definition;
      $deleted_storage_definition->setDeleted(TRUE);
      $this->deletedFieldsRepository->addFieldDefinition($deleted_storage_definition);
      $this->deletedFieldsRepository->addFieldStorageDefinition($deleted_storage_definition);
    }

    if ($storage instanceof FieldStorageDefinitionListenerInterface) {
      $storage->onFieldStorageDefinitionDelete($storage_definition);
    }

    $this->entityLastInstalledSchemaRepository->deleteLastInstalledFieldStorageDefinition($storage_definition);

    $this->eventDispatcher->dispatch(new FieldStorageDefinitionEvent($storage_definition), FieldStorageDefinitionEvents::DELETE);