I want to give a heads-up to all those just beginning with AS3 about how it handles memory. I had to find out about this the hard way, and now have to redo a lot of stuff.
Flash Player 9 introduced a new system management feature called a garbage collector (GC). Basically, what it does is “sweep” for objects that can not be used/accessed anymore, and delete them, freeing memory. Until those ‘null’ objects are removed by the GC, they will sit in memory until the Player is closed.
So, whenever you want something to be deleted (escpecially with CPU intensive particle systems), you must be aware of what and where you are referencing your objects, so you could easily remove them. You have to do this by hand. One method is to set all objects you want to delete, and all references to it, to null. Even then, you have to wait for the GC to do its “sweeping motion” for those objects to be deleted.
Another thing to watch out for are event listeners. Make sure you remove any listeners (by calling removeEventListener()) from objects you want to delete, since they also hold a reference to your objects.
Check this article series for more details and info about the GC and resource management in Flash Player 9/AS3.
And lastly, it is about unloading external swf’s through Loader. You might think that using unload() from a Loader would remove that swf completely, but that isn’t the case. In fact, unload() does a pretty poor job at “unloading” swfs. Here is a quote from another article that explains this in great detail:
In AS3, calling Loader.unload() simply removes the reference to the loaded movie. If any other references exist to the loaded content, it will not be unloaded.
My site has been delayed by almost a month now, trying to figure out and fix my memory leak problem. I finally have an idea of what’s wrong, now I have to figure out a solution.
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