User Guide

Scoping in custom components 83

For example, the following example sets the horizontalPageScrollSize property and a

listener for the

scroll event for your custom control, but you cannot specify properties for

the child CheckBox or Tex tI np u t controls of the Form container:

<?xml version="1.0"?>

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"

xmlns:MyComp="*">

<mx:Script>

<![CDATA[

import mx.events.ScrollEvent;

private function handleScrollEvent(event:ScrollEvent):void {

// Handle scroll event.

}

]]>

</mx:Script>

<MyComp:AddressForm horizontalPageScrollSize="25"

scroll="handleScrollEvent(event);"/>

</mx:Application>

To configure the children of a custom MXML component, you define new properties in the

MXML component, and then use those new properties to pass configuration information to

the component children. For more information, see Chapter 8, “Creating Advanced MXML

Components,” on page 91.

Scoping in custom components

Scoping is mostly a description of what the this keyword refers to at any given point in your

application. In an

<mx:Script> tag in an MXML file, the this keyword always refers to the

current scope. In the main application file, the file that contains the

<mx:Application> tag,

the current scope is the Application object; therefore, the

this keyword refers to the

Application object.

In an MXML component, Flex executes in the context of the custom component. The

current scope is defined by the root tag of the file. So, the

this keyword refers not to the

Application object, but to the object defined by the root tag of the MXML file.

For more information on scoping, see Chapter 4, “Using ActionScript,” in Flex 2 Developer’s

Guide.