Example of flex-extensions InvalidationTracker. See: https://github.com/johnyanarella/flex-extensions/

InvalidationTrackerExampleComponent.as

package
{
	import com.codecatalyst.util.invalidation.InvalidationTracker;
	
	import mx.core.UIComponent;
	
	public class InvalidationTrackerExampleComponent extends UIComponent
	{
		// ========================================
		// Protected properties
		// ========================================
		
		/**
		 * Invalidation tracker.
		 */
		protected var tracker:InvalidationTracker = null;
		
		// ========================================
		// Public methods
		// ========================================
		
		[Invalidate("properties")]
		[Bindable]
		/**
		 * First property.
		 */
		public var first:String;
		
		[Invalidate("displaylist,properties,size")]
		[Bindable]
		/**
		 * First property.
		 */
		public var second:String;
		
		// ========================================
		// Constructor
		// ========================================
		
		/**
		 * Constructor.
		 */
		public function TestComponent()
		{
			super();
			
			tracker = new InvalidationTracker( this );
		}
		
		// ========================================
		// Protected methods
		// ========================================
		
		/**
		 * @inheritDoc
		 */
		override protected function measure():void
		{
			super.measure();
			
			if ( tracker.invalidated( "second" ) )
			{
				trace( "Second invalidated." );
			}
		}
		
		/**
		 * @inheritDoc
		 */
		override protected function commitProperties():void
		{
			super.commitProperties();
			
			if ( tracker.invalidated( "first" ) )
			{
				trace( "First invalidated - previous value: " + tracker.previousValue( "first" ) + " current value: " + first );
			}
			
			if ( tracker.invalidated( "second" ) )
			{
				trace( "Second invalidated - previous value: " + tracker.previousValue( "second" ) + " current value: " + second );
			}
			
			if ( tracker.invalidated() )
			{
				trace( "A tracked property was invalidated." );
			}
			
			// No longer required - InvalidationTracker will automatically reset() invalidated properties in response to FlexEvent.UPDATE_COMPLETE.
			// tracker.reset( "first" );
		}
		
		/**
		 * @inheritDoc
		 */
		override protected function updateDisplayList( unscaledWidth:Number, unscaledHeight:Number ):void
		{
			super.updateDisplayList( unscaledWidth, unscaledHeight );
			
			if ( tracker.invalidated( "second" ) )
			{
				trace( "Second invalidated." );
			}
			
			// No longer required - InvalidationTracker will automatically reset() invalidated properties in response to FlexEvent.UPDATE_COMPLETE.
			// tracker.reset( "second" );
		}
	}
}