Ginger Binger

I was talking with Ido about memory usage in AS3, and we discovered a small weakness in the AVM’s garbage collector. If you use a functional style of programming with lots of anonymous or nested functions, here’s something to watch out for:

import flash.display.Sprite;
import flash.events.Event;

function foo():* {
    var sprite:Sprite = new Sprite();
    sprite.addEventListener(Event.ENTER_FRAME, tick);

    // this closure creates a reference to the outer scope, foo
    return function():void { }
}

function tick(event:Event):void {
    trace("tick");
}

var func:* = foo();
System.gc();
// sprite is never garbage collected, and continues to tick

sprite will not be garbage collected, even though it’s just a local variable of foo and no other references to it exist!

[click to continue…]

{ 1 comment }