Adding/Deleting HABTM on existing records

Hi, I have searched this forum and read the manuals, and finally got
my code working, BUT am I doing this right or have I just found a
cludge by dumb luck?

I have 2 tables Questions and Games joined correctly thru
games_questions table. Users can attach or detach Questions from a
Game (drag 'n drop) but I was having trouble writing/deleting into the
games_questions x-ref.

The post on this forum titled "not understanding simple HABTM save/
delete" by Ryan McKillen gave me my solution (adapted version below),
along with http://teknoid.wordpress.com/2008/07/11/notes-on-cakephp-habtm-part-2-saving-data/

So my question is: Do I have to read the existing relationships ($this-
>Question->find) just to insert/remove a new relationship? I have used
containable to make the read as efficient as possible, but it seems
wasteful.

If I don't populate the array then all existing relationships get
replaced by the new one, and this is the only way I found to get it to
work.

//Read the existing Question to get current relationships...
$data=$this->Question->find('first',array(
'conditions'=>array('Question.id'=>$q_id),
'contain'=>array('Game.id')
));
// Extract only the Game's ids into an array
$existing=Set::extract('/Game/id',$data);
// Build a new datastructure
$this->data['Question']['id']=$q_id;
$this->data['Game']=$existing;
$this->data['Game'][]=$target_game_id'];

if ($this->Question->save($this->data)){
/// Yay it saved
}

I haven't written the code to Detach a Question from a Game yet, but
unless I hear otherwise I guess I'll do something similar:
1. Read existing relationships
2. Remove the target from the array
3. Save the Question (the delete would be implied)

Somehow it seems unnatural IMO to use Save on a model to Insert, Save,
and Delete HABTM relationships, but I'll get used to it, if that's
what it takes.

Thanks folks.
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