Macromedia flex 2 Manual

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Creating Simple Visual Components in ActionScript

The one place where Flex prohibits the use of a default property is when you use the 
ActionScript class as the root tag of an MXML component. In this situation, you must use 
child tags to define the property, as the following example shows:

<?xml version="1.0"?>
<!-- as/myComponents/TextAreaDefaultPropMXML.mxml -->
<MyComp:TextAreaDefaultProp xmlns:mx="http://www.adobe.com/2006/mxml" 
    xmlns:MyComp="myComponents.*">

        <MyComp:defaultText>Hello</MyComp:defaultText>
        
</MyComp:TextAreaDefaultProp>

Making properties accessible in Flex Builder

You can make your property definitions accessible in Flex Builder by adding the 

[Inspectable]

 metadata tag to the property definition. For example, if you are using Adobe 

Flex Builder, you can insert the 

[Inspectable]

 metadata tag to define the property as user-

editable (or inspectable), as the following example shows:

[Inspectable]
var prop1:Number;

You can also use the 

[Inspectable]

 metadata tag with setter and getter methods. For more 

information, see 

. 

Using data binding with custom properties

Data binding defines a syntax for automatically copying the value of a property of one object, 
the source property, to a property of another object, the destination property, at run time. Data 
binding is usually triggered when the value of the source property changes.

The following example shows a Text control that gets its data from a 

Slider

 control’s 

value

 

property. The property name inside the curly braces ({ }) specifies a binding expression that 
copies the value of the source property, 

mySlider.value

, into the destination property, the 

Text

 control’s 

text

 property.

<mx:Slider id="mySlider"/>
<mx:Text text="{mySlider.value}"/>

Using properties as the destination of a binding expression

Properties in your custom components can take advantage of data binding. Any property 
defined as a variable or defined by using a setter and getter method can automatically be used 
as the destination of a binding expression.