Dynamically Build a SQL Where Clause with the IN Keyword - cakephp

Question

I'm using cakephp 2.3.0. Summary - In my controller, I have a query where it returns one or more id values. Then, I want to use those id values in my next query, with the SQL IN keyword. I know conceptually what I want to accomplish. I think I'm doing this the correct way in CakePHP, but I could be wrong. I'm just not sure on the coding piece to dynamically build my IN clause.
Here is my code snippet from my controller:
$this->set('userIDs', $this->Activity->ActivitiesOfInterest->find('all',
array (
'conditions' => array ('ActivitiesOfInterest.activities_id' => $id),
'fields' => array ('ActivitiesOfInterest.user_id'))));
The above code is fine as I get the value or values that I would expect. In the code below, I have hard-coded this piece, array(3, 4), which is equivalent to the SQL IN keyword. The values 3, 4 would be stored in the userIDs array. But, this is where I'm not sure how to dynamically build the values of 3 and 4, from the array in the above code. Of course, 3 and 4 may not always be the values because it just depends on what is in the database. I think I need to loop through the array and build up my list of id's. I'm still somewhat new to CakePHP and I'm guessing this is an easy answer for the experienced folks.
And, yes I actually do want to perform a deleteAll operation, based on my use case.
$this->Activity->ActivitiesOfInterest->deleteAll(
array('ActivitiesOfInterest.user_id' => array(3, 4)), false);
Thank you, much appreciated.

Answer 1

You can also do this by using sub query for deleteALL query.
$conditionsSubQuery['ActivitiesOfInterest.activities_id'] = $id;
$db = $this->Financial->getDataSource();
$subQuery = $db->buildStatement(
array(
'fields' => array('ActivitiesOfInterest.user_id'),
'table' => $db->fullTableName($this->Activity->ActivitiesOfInterest),
'alias' => 'ActivitiesOfInterest',
'offset' => null,
'joins' => array(),
'conditions' => $conditionsSubQuery,
'order' => null,
'group' => null
),$this->Activity->ActivitiesOfInterest
);
$subQuery = ' ActivitiesOfInterest.user_id IN (' . $subQuery . ')' ;
$subQueryExpression = $db->expression($subQuery);
$conditions[] = $subQueryExpression;
$result = $this->Activity->ActivitiesOfInterest->deleteAll(compact('conditions'));

Answer 2

You don't need to use $this->set(), unless you need those user-ids inside your view;
The Hash::extract() may be helpfull here.
// Find the user-ids
$result = $this->Activity->ActivitiesOfInterest->find('all', array (
'conditions' => array (
'ActivitiesOfInterest.activities_id' => $id
),
'fields' => array (
'ActivitiesOfInterest.user_id'
)
));
if ($result) {
// 'extract' just the user-ids from the results
$userIds = Hash::extract($result, '{n}.ActivitiesOfInterest.user_id');
$this->Activity->ActivitiesOfInterest->deleteAll(
array(
'ActivitiesOfInterest.user_id' => $userIds
),
false
);
}