Question

I would love to sort an embedded MongoDB object using PHP Lithium. I have got a Model “Thread” which looks almost like this:

{
   "_id": ObjectId("4f71bf4618b602580f000009"),
   "postings": [
      {text: "a", upvotes: 15, /*...*/},
      {text: "b", upvotes: 23},
      {text: "c", upvotes: 16},
      {text: "d", upvotes: 42}
   ],
   // bla
}

Now I would like to sort the postings depending on their upvotes. I already wrote a method which roughly does what I want:

public function postings_sort_by_upvotes($thread) {
    $postings = $thread->postings->to('array');
    usort($postings, function($a, $b) {
                         return ($a['upvotes'] > $b['upvotes'] ? 1 : -1);
                     });
    return $postings;
}

This works, but obviously it returns the postings as a plain array, while the unsorted postings were a lithium\data\collection\DocumentArray type.

Do I really need to struggle with an array instead of an object or is there a way which allows me to sort them without losing the original data type?

Answer 1

A DocumentArray object is a Collection, and hopefully, Lithium Collections are sortable.
You can call sort() on a $collection different ways :

$collection->sort('field'); //sort naturally by the given field

Or define a custom closure :

$collection->sort(function ($a,$b) {
    if ($a == $b) {
        return 0;
    }
    return ($b > $a ? 1 : -1);
});

Check docs on lithium\data\Collection, from which DocumentArrayinherits, and lithium\util\Collection, the Collection object.

an Introduction to Collectionsby Joe Beeson. He don’t cover sorting especially but it worth a read (other articles too)