Adobe FLEX 2 - CREATING AND EXTENDING COMPONENTS Manual page 135

When you define a property by using getter and setter methods so that the property is usable
as the source for data binding, you include the
method, and optionally include the name of the event dispatched by the setter method when
the property changes, as the following example shows:
package myComponents
{
// as/myComponents/TextAreaFontControlBinding.as
import mx.controls.TextArea;
import flash.events.KeyboardEvent;
import flash.events.Event;
public class TextAreaFontControlBinding extends TextArea
{
public function TextAreaFontControlBinding()
{
super();
addEventListener("keyDown", myKeyDown);
addEventListener("creationComplete", myCreationComplete);
}
private var currentFontSize:Number;
public var minFontSize:Number = 5;
// Define private variable for maxFontSize.
public var _maxFontSize:Number = 15;
// Define public getter method, mark the property
// as usable for the source of data binding,
// and specify the name of the binding event.
[Bindable("maxFontSizeChanged")]
public function get maxFontSize():Number {
return _maxFontSize;
}
// Define public setter method.
public function set maxFontSize(value:Number):void {
if (value <= 30) {
_maxFontSize = value;
} else _maxFontSize = 30;
// Dispatch the event to trigger data binding.
dispatchEvent(new Event("maxFontSizeChanged"));
}
private function myCreationComplete(eventObj:Event):void {
// Get current font size
currentFontSize = getStyle('fontSize');
}
metadata tag before the getter
[Bindable]
Adding properties and methods to a component 135