Hash::extract with HABTM - cakephp

Question

I'm having difficulty understanding the syntax of Hash::extract when dealing with HABTM.
I have data coming back from a find() that looks like this:
array(
(int) 0 => array(
'EventsGroup' => array(
'id' => '34',
'event_id' => '5',
'group_id' => '1'
)
),
(int) 1 => array(
'EventsGroup' => array(
'id' => '29',
'event_id' => '2',
'group_id' => '1'
)
)
)
I'm trying to get to an array that looks like: array(x,y,z) where x,y,z are event_id's.
The Cake documentation's example looks like:
$users = $this->User->find("all");
$results = Hash::extract($users, '{n}.User.id');
Based on that, I tried:
$eventsGroups = $this->EventsGroup->findAllByGroupId($groupid);
$secEvents = Hash::extract($eventsGroups, '{n}.{EventsGroup}.event_id' );
$secEvents2 = Hash::extract($eventsGroups, '{n}.EventsGroup.event_id' );
$secEvents3 = Hash::extract($eventsGroups, '{n}.[text=EventsGroup].event_id);
None of which worked.
I found a way to get what I wanted without using Hash::extract, but I'd like to use it as some of the other methods will be useful to me down the road.
Any help or pointers would be greatly appreciated!
Thanks

Answer 1

Have you tried:
$eventsGroups = $this->EventsGroup->findAllByGroupId($groupid);
$secEvents = Hash::extract($eventsGroups, '{n}.EventsGroup[event_id]' );
As the docs says to retrieve a field you should use a matcher and not a expression. And the brackets ({}) are not needed, they are used to build expressions like '{n}.{s}'...