Creating weak references in Actionscript 3

15th August 2007

It’s great that Actionscript 3 has weak references in the EventDispatcher and Dictionary classes. But sometimes you want to create your own weak references. Something along the lines of

var weak:WeakRef = new WeakRef( someObject );

Well, there is a way. It’s a bit of a hack, and unfortunately uses a full Dictionary object for each weak reference, but it works. The source code is very short:

package
{
    import flash.utils.Dictionary;
	
    class WeakRef {
        private var dic:Dictionary;
		
        public function WeakRef( obj:* ) {
            dic = new Dictionary( true );
            dic[obj] = 1;
        }
		
        public function get():* {
            for( var item:* in dic ) {
                return item;
            }
            return null;
        }
    }
}

Download the WeakRef class.

To use it

// Create a weak reference
var weak:Weakref = new WeakRef( obj );

// Use the referenced object
var strong = weak.get();
if( strong != null ) {
    // use strong here
} else {
    // garbage collector has disposed of the object
}

The source is free under the terms of the MIT licence. Please download the source file rather than copying and pasting since it contains the licence notice and useful comments.

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