[Codemonkey]

 
A lot of the time while debugging/profiling, you'll be interested in how many FPS your movie is actually pulling to see if there's something slowing it down.

Here's a class that let's you specify the update interval and invokes a method each time. You can drop this class in a util folder and use it in any of your projects:

import mx.utils.Delegate;
 
class util.FPS {
    private static var instance:FPS;
    private var time:Number;
    private var counter:Number;
    private var interval:Number;
    private var dummy:MovieClip;
    
    public var onUpdate:Function;
    
    public function FPS(interval:Number) {
        var d:Number = _root.getNextHighestDepth();
        this.dummy = _root.createEmptyMovieClip("fpsmc" + d, d);
        this.interval = interval;
        this.start();
    }
 
    // reset and start measuring
    public function start() {
        counter = 0;
        time = getTimer();
        dummy.onEnterFrame = Delegate.create(this, measure);
    }
 
    public function stop() {
        dummy.onEnterFrame = null;
        delete dummy.onEnterFrame;
    }
 
    // checks whether it should perform a measurement
    private function measure() {
        var now:Number = getTimer();
        var lapsed:Number = now - time;
        if (lapsed >= interval) {
            onUpdate(counter * (1000 / lapsed));
            time = now;
            counter = 0;
        }  
        counter++;
    }
} 

To use it:

import util.FPS;
 
// create FPS meter and update every 500ms
var fps:FPS = new FPS(500);
fps.onUpdate = function(fps:Number) {
    trace(fps);
} 

Don't set the interval too low though (min. 250ms) or the measurements become unreliable.