const Tasklist Tasklist::filter(bool filterByID = false, int IDMin = 0, int IDMax = 0,
                                bool filterByDateOfCreation = false, QString dateOfCreationMin = "", QString dateOfCreationMax = "",
                                bool filterByPriority = false, int priorityMin = 0, int priorityMax = 0,
                                bool filterByDone = false, bool done = false)
{
  QVector<Task> filtered_list(tasks.size());

  auto condition_checker = [](Task t){
      return ( ( filterByID ? isBetveen( t.getID(), IDMin, IDMax )  : true ) &&
               ( filterByDateOfCreation ? isBetveen( t.getDateOfCreation(), dateOfCreationMin, dateOfCreationMax ) : true ) &&
               ( filterByPriority ? isBetveen( t.getPriority(), priorityMin, priorityMax ) : true ) &&
               ( filterByDone ? ( t.getDone() == done ) : true )
            );
    };

  auto it = std::copy_if( tasks.begin(), tasks.end(), filtered_list.begin(), condition_checker );
  filtered_list.resize( std::distance(filtered_list.begin(), it) );  // shrink container to new size

  return Tasklist( filtered_list );
}