Flex 3 Cookbook

Chapter 14. Data Binding

The Flex Framework provides a robust structure for architecting component-driven applications. Within this powerful framework is an event-based system in which objects can subscribe to updates of property values on other objects by using data binding.

Data binding provides a convenient way to pass data between different layers within an application, by linking a source property to a destination property. Changes to properties on a destination object occur after an event is dispatched by the source object to notify all destination objects of an update. With the property on a source object marked as bindable, other objects can subscribe to updates by using a destination property. To enable data binding on a property, you must define the [Bindable] metadata tag in one of three ways:

• Before a class definition:

  package com.oreilly.flexcookbook
  {
      import flash.events.EventDispatcher;
  
      [Bindable]
      public class DataObject extends EventDispatcher{}
  }

  Adding a [Bindable] tag prior to a class definition establishes a binding expression for all public attributes held on that class. Classes using binding must be an implementation of IEventDispatcher because data binding is an event-based notification system to copy source properties to destination properties.

• Before a public, protected, or private variable:

  [Bindable] private var _lastName:String;
  [Bindable] protected var _age:Number;
  [Bindable] public var firstName:String;

  Bindable variables marked as private are available for ...