Question

Can anybody say me what is faster: Array or ArrayList? (ActionScript3)

I tried to find a page about this but didn’t find anything.
Thank you.

Answer 1

As already stated, Array is faster. Actually it is orders of magnitude faster.

The equivalents of array access are getItemAt and setItemAt.

Implementation:

public function getItemAt(index:int, prefetch:int = 0):Object
{
    if (index < 0 || index >= length)
    {
        var message:String = resourceManager.getString(
            "collections", "outOfBounds", [ index ]);
        throw new RangeError(message);
    }

    return source[index];
}

and:

public function setItemAt(item:Object, index:int):Object
{
    if (index < 0 || index >= length) 
    {
        var message:String = resourceManager.getString(
            "collections", "outOfBounds", [ index ]);
        throw new RangeError(message);
    }

    var oldItem:Object = source[index];
    source[index] = item;
    stopTrackUpdates(oldItem);
    startTrackUpdates(item);

    //dispatch the appropriate events 
    if (_dispatchEvents == 0)
    {
        var hasCollectionListener:Boolean = 
            hasEventListener(CollectionEvent.COLLECTION_CHANGE);
        var hasPropertyListener:Boolean = 
            hasEventListener(PropertyChangeEvent.PROPERTY_CHANGE);
        var updateInfo:PropertyChangeEvent; 

        if (hasCollectionListener || hasPropertyListener)
        {
            updateInfo = new PropertyChangeEvent(PropertyChangeEvent.PROPERTY_CHANGE);
            updateInfo.kind = PropertyChangeEventKind.UPDATE;
            updateInfo.oldValue = oldItem;
            updateInfo.newValue = item;
            updateInfo.property = index;
        }

        if (hasCollectionListener)
        {
            var event:CollectionEvent =
                new CollectionEvent(CollectionEvent.COLLECTION_CHANGE);
            event.kind = CollectionEventKind.REPLACE;
            event.location = index;
            event.items.push(updateInfo);
            dispatchEvent(event);
        }

        if (hasPropertyListener)
        {
            dispatchEvent(updateInfo);
        }
    }
    return oldItem;    
}

There’s a LOT of calls and checks involved here. Please note, that _dispatchEvents == 0 is true by default (unless you disableEvents), thus writing in fact is an immense operation.

However ArrayList does provide a lot of feature, that are usefull within flex. A good compormise is to grab the underlying Array (accessible as ArrayList::source), peform your operations, and then reassign it (supposing you have listeners observing that Array).

Also, if you go with Flash Player 10, then Vector will outperform Array.

greetz
back2dos