我必须实现哪个SPL接口才能在对象上使用usort（）函数？

Question

I have a class that represents a collection entity : it has only one attribute, an array. This class implements \Countable, \IteratorAggregate, and the most important for this question, \ArrayAccess.

But when using :

        usort($collectionData, function($a, $b) {
            return ($a->getPosition() > $b->getPosition());
        });

I get the following catchable exception :

Warning: usort() expects parameter 1 to be array, object given in /home/alain/workspace/(...)n.php line 1057 (500 Internal Server Error)

I can trick using an intermediate variable :

        $data = $collectionData->getData();
        usort($data, function($a, $b) {
            return ($a->getPosition() > $b->getPosition());
        });
        $collectionData->setData($data);

But wanted to know if there is an SPL interface that can pass through the array parameter type expectation of usort().

Answer 1

Not that I know of. No interface will make your object be also an array and that's what you need to pass to usort(). However you can encapsulate this behaviour in your class by adding usort() method to your class.

class CollectionEntity implements Countable, IteratorAggregate, ArrayAccess {

  private $data = array();

  /* other methods omitted for simplicity */

  public function usort(Closure $callback) {
    usort($this->data,$callback);
  }


}