Macromedia flex 2 Manual

Scoping in custom components

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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 

TextInput

 controls of the Form container:

<?xml version="1.0"?>
<!-- mxml/MainEmptyFormProps.mxml-->
<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 

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.