MigrateRowDeleteEvent example

$id_map = $this->getIdMap();
    $destination = $this->migration->getDestinationPlugin();

    // Loop through each row in the map, and try to roll it back.     $id_map->rewind();
    while ($id_map->valid()) {
      $destination_key = $id_map->currentDestination();
      if ($destination_key) {
        $map_row = $id_map->getRowByDestination($destination_key);
        if (!isset($map_row['rollback_action']) || $map_row['rollback_action'] == MigrateIdMapInterface::ROLLBACK_DELETE) {
          $this->getEventDispatcher()
            ->dispatch(new MigrateRowDeleteEvent($this->migration, $destination_key), MigrateEvents::PRE_ROW_DELETE);
          $destination->rollback($destination_key);
          $this->getEventDispatcher()
            ->dispatch(new MigrateRowDeleteEvent($this->migration, $destination_key), MigrateEvents::POST_ROW_DELETE);
        }
        // We're now done with this row, so remove it from the map.         $id_map->deleteDestination($destination_key);
      }
      else {
        // If there is no destination key the import probably failed and we can         // remove the row without further action.         $source_key = $id_map->currentSource();