class Buildings extends Nette\Object
{
    const BUILDING_MARKET = 1;
    const BUILDING_BARRACKS = 2;
    // ...

    public function fetchBuildingCrop($building, $fetchColumn = 'attri')
    {
        return $this->repositories->building_level
            ->select()->where('building_id = %i', $building)
            ->fetchPairs('level', $fetchColumn);
    }
}