Invalidate Pattern example

InvalidationPattern.as

package
{
	import flash.display.Shape;
	import flash.events.Event;
	
	public class InvalidationPattern
	{
		protected const USE_DEFERRED_VALIDATION:Boolean = true;
		
		protected var tickerShape:Shape;
		protected var needsValidation:Boolean;
		protected var _property:int;
		
		/** Constructor. **/
		public function InvalidationPattern()
		{
			// shapes always get enter frame events, no stage required
			tickerShape = new Shape();
			tickerShape.addEventListener(Event.ENTER_FRAME, onEnterFrame);
		}

		/** An example property. **/
		public function get property():int { return _value; }
		public function set property(value:int):void
		{
			if (value != _property)
			{
				_property = value;
				invalidate();
			}
		}
		
		/** Invalidates object. **/
		public function invalidate():void
		{
			needsValidation = true;
			if (USE_DEFERRED_VALIDATION) return; // don't do anything yet
			validate();
		}
		
		/** Validates an object. **/
		public function validate():void
		{
			// if any of your dependent properties are not set,
			// just exit this method now and it'll be called later
			// if they're all ready, process the properties and
			// update the state of the object
			needsValidation = false;
		}

		/** Enter frame handler. **/
		protected function onEnterFrame(event:Event):void
		{
			if (needsValidation) validate();
		}
	}
}