Question

I have an SplObjectStorage instance that stores element objects to be rendered in a container. I would like the ability to efficiently add and remove objects from any random position in the store.

Example:

<?php
$store = new SplObjectStorageWrapper;
$obj1 = new Obj;
$obj2 = new Obj;
$obj3 = new Obj;

$store->attach($obj1);
$store->attach($obj2);
$store->insertAtIndex($obj3, 1);

//Storage should now be organized as $obj1, $obj3, $obj2

How would I go about implementing the insertAtIndex method? Do I use a LimitIterator to detach and reattach children after a certain position? Using an array-based object storage has proven to be much slower than an SplObjectStorage instance.

Other methods that I would like to implement include removeAtIndex(integer) and indexOf(object)

Answer 1

It turns out the easiest (and apparently most efficient) way to do this is to extend SplObjectStorage and to make use of LimitIterator. Code example below:

<?php
/**
 * Extends the SplObjectStorage class to provide index functions
 */
class ObjectStorage extends SplObjectStorage {

    /**
     * Returns the index of a given object, or false if not found
     * @param object $object
     */
    function indexOf($object){

        if(!$this->contains($object)) return false;

        foreach($this as $index => $obj) if($obj === $object) return $index;

    }

    /**
     * Returns the object at the given index
     */
    function itemAtIndex($index){

        $it = new LimitIterator($this, $index, 1);
        foreach($it as $obj) return $obj;

    }

    /**
     * Returns the sequence of objects as specified by the offset and length
     * @param int $offset
     * @param int $length
     */
    function slice($offset, $length){

        $out = array();
        $it = new LimitIterator($this, $offset, $length);
        foreach($it as $obj) $out[] = $obj;
        return $out;

    }

    /**
     * Inserts an object (or an array of objects) at a certain point
     * @param mixed $object A single object or an array of objects
     * @param integer $index
     */
    function insertAt($object, $index){

        if(!is_array($object)) $object = array($object);

        //Check to ensure that objects don't already exist in the collection
        foreach($object as $k => $obj):
            if($this->contains($obj)) unset($object[$k]);
        endforeach;

        //Do we have any objects left?
        if(!$object) return;

        //Detach any objects at or past this index
        $remaining = array();
        if($index < $this->count()):
            $remaining = $this->slice($index, $this->count() - $index);
            foreach($remaining as $obj) $this->detach($obj);
        endif;

        //Add the new objects we're splicing in
        foreach($object as $obj) $this->attach($obj);

        //Attach the objects we previously detached
        foreach($remaining as $obj) $this->attach($obj);

    }

    /**
     * Removes the object at the given index
     * @param integer $index
     */
    function removeAt($index){

        $this->detach($this->itemAtIndex($index));

    }

}