/**
* Adds a topic to this date.
*
* @param mixed $topic Topic definition (might be an id, an array or an
* object)
* @return number addition of all return values, false if none was called
*/
public function addTopic($topic)
{
$topic = CourseTopic::toObject($topic);
if (!$this->topics->find($topic->id)) {
$this->topics[] = $topic;
return $this->storeRelations('topics');
}
}
