Flex 4 Cookbook

Chapter 13. 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, notifying all destination objects of an update. With the property on a source object marked as bindable, other objects can subscribe to updates by assigning 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.f4cb
{
    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 readable and writable public attributes held on that class. Classes using binding must implement the IEventDispatcher interface because data binding is an event-based notification system for copying 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 ...