public function canBeDeleted()
{
$criteria = new Criteria();
$criteria->add(CourseSubjectDayPeer::CLASSROOM_ID, $this->getId());
return CourseSubjectDayPeer::doCount($criteria) == 0;
}
public function isConfiguredToCourse($day_number)
{
$c = new Criteria();
$c->add(CourseSubjectDayPeer::COURSE_SUBJECT_ID, $this->getId());
$c->add(CourseSubjectDayPeer::DAY, $day_number);
return CourseSubjectDayPeer::doCount($c) > 0;
}