sort Magento collection AFTER load

Question

The Magento collection sorting functions (e.g. Mage_Eav_Model_Entity_Collection_Abstract::addAttributeToSort) work by adding an ORDER BY clause to the SQL select statement. However, there are times when a collection has already been loaded and it is necessary to sort the collection.

It is certainly possible to use the toArray($fields) function and then PHP array sorting functions (either native or user-defined), however this is a little clumsy. It also means that the objects in the collection are converted to "dumb" rows of values without magic getters/setters which can/are be implemented with algorithms, etc.

I'm wondering if there are more elegant/Magento-esque methods of sorting the collection.

Thanks,
Jonathan

Solution 1

Another solution which works:

class Aligent_Navigation_Block_Dropdown extends Mage_Catalog_Block_Product_List {

public function getProductsByShortDesc(){
    $data = $this->getLoadedProductCollection()->getItems();  //an array of objects
    usort($data,array('Aligent_Navigation_Block_Dropdown','sortByShortDesc'));
    return $data;
}

public static function sortByShortDesc($a, $b)
{
  if($a->getShortDescription() ==  $b->getShortDescription()){ return 0 ; }
  return ($a->getShortDescription() < $b->getShortDescription()) ? -1 : 1;
}
}

Solution 2

There is no proper way of doing it. But I think it is possible with using of Reflection. You can retrieve $_items property of collection object, sort them and set it back to the collection.

function sortCollection(Varien_Data_Collection $collection, callable $sorter) {
    $collectionReflection = new ReflectionObject($collection);
    $itemsPropertyReflection = $collectionReflection->getProperty('_items');
    $itemsPropertyReflection->setAccessible(true); // Make it accessible

    $collectionItems = $itemsPropertyReflection->getValue($collection);

    usort($collectionItems, $sorter);

    $itemsPropertyReflection->setValue($collection, $collectionItems);

    $itemsPropertyReflection->setAccessible(false); // Return restriction back

    return $collection;
}

Solution 3

Here's a tip; A collection's clear method unsets it's loaded flag, it allows you to change the sort or filters and run the new query.

I accidentally discovered it when answering load only configurable products.

Solution 4

The method of @Ivan Chepurnyi worked but returns a ReflectionObject object, in my case I needed a Varien_Data_Collection.
Here is what I did instead

$collectionItems = $collection->getItems();
usort($collectionItems, array($this, '_sortItems'));
$newCollection = new Varien_Data_Collection();

foreach ($collectionItems as $item) {
    $newCollection->addItem($item);
}

var_dump($newCollection);

And in case here is the sorting method

public function _sortItems($a, $b)
{
    $columnId = "your_column_that_you_need_to_sort";
    $dir      = "desc";

    $al = strtolower($a->getData($columnId));
    $bl = strtolower($b->getData($columnId));

    if ($al == $bl) {
        return 0;
    }

    if ($dir == 'asc') {
        return ($al < $bl) ? -1 : 1;
    } else {
        return ($al > $bl) ? -1 : 1;
    }
}

View more solutions

Comments

[OSdave]

I confirm it's possible Ivan, my partner just use your snippet succesfully. The only thing is that instead of $collection->getProperty('_items'); he had to use $collectionReflection->getProperty('_items');, a small typo I guess. One another thing I think worth telling, is that, as we're talking about Magento, and thus Classes, $yourSortingCallback has to be an array of 2 elements, first one being the name of the class where the method is defined, and 2nd one is the name of the method, ie: usort($collectionItems, array('The_Class', 'The_Method'));. Anyway, we're both very thankfull

[Ivan Chepurnyi]

@OSdave, yeah there was a type. $yourSortingCallback call back can be even anonymous function.

[benz001]

and of course it means you can also addAttributeToSelect() as well, which was just what I was struggling with, thanks :-)

[Kasper Sanguesa-Franz]

Only problem with this solution is if you got multiple pages then this would sort only the items on this page