<?php
Builder::macro('orderByRelation', function(string $searchColumn, string $dir) {
            list($relation, $column) = explode('.', $searchColumn);
            $relation_table = $this->getRelation($relation)->getModel()->getTable();
            $relation_foreign_key = $this->getRelation($relation)->getForeignKeyName();
            $query_table = $this->getModel()->getTable();

            $this->select($query_table . '.*')
                ->join($relation_table, $query_table . '.' . $relation_foreign_key, '=', $relation_table . '.id')
                ->orderBy($relation_table . '.' . $column, $dir);
            
            return $this;
        });