How to return an empty Doctrine_Collection? - php

Question

I've a method that returns a Doctrine_Collection, with a whereIn() clause :
public function getByValues($values)
{
if (!is_array($values))
throw new sfException('Wrong parameter type. Excepted array.');
return Doctrine_Query::create()
->from('Anomaly a')
->whereIn('a.value', $values);
}
However, when $values is an empty array, this method return all the rows that are in the AnomalyTable. This isn't an unexpected behavior, as documented in Doctrine documentation, and written here : Doctrine where in with Doctrine_Query
However, I would like to return an empty Doctrine_Collection instead of the result of my query, when $values is an empty array.
Any ideas on how I can do that ?
Thanks =)
Edit:
Adding an impossible clause, like ->where('1=0') would do the trick, but it is an unnecessary request to the DB server. Does anyone have a better idea ?

Answer 1

And what about (you need also the execute method to get the result of the query ! with that the return type will be the same everytime) :
public function getByValues($values)
{
if (!is_array($values))
throw new sfException('Wrong parameter type. Excepted array.');
if (empty($values)) {
return new Doctrine_Collection('Anomaly');
}
return Doctrine_Query::create()
->from('Anomaly a')
->whereIn('a.value', $values)
->execute()
;
}

Answer 2

By value, I assume you mean $values right? just add something to check if values is empty and then manually supply an empty collection.
if(empty($values))
return Doctine_Query::create()->from('Anomaly a')->where('1=0');

Answer 3

if(count($values)){
return Doctrine_Query::create()
->from('Anomaly a')
->whereIn('a.value', $values);
} else {
return Doctine_Query::create()
->from('Anomaly a')
->where('0=1');
}

Answer 4

I think it's impossible to do that.
The Doctrine_Collection is more than a resultset/array of objects. It also has means of deleting and adding objects and keeping that state.
That's probably also why many native Doctrine functions return FALSE when no results were found. (For instance, the NestedSet functions).
So, for you it's probably best to return FALSE as well. or maybe an empty array. Both arrays as Doctrine_Collection can be used in a foreach loop and count function.
Should you want to use the delete and add functions, you could just call the constructor.

Answer 5

I personnaly use the following trick:
public function getByValues($values)
{
if (!is_array($values))
throw new sfException('Wrong parameter type. Excepted array.');
$values = empty($values) ? array(-1) : $values;
return Doctrine_Query::create()
->from('Anomaly a')
->whereIn('a.value', $values);
}
Works great even if somewhat hackish.