Macromedia flex 2 Manuale

Adding properties and methods to a component

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For example, in the section 

created a class with the public property 

maxFontSize

. You can use the 

maxFontSize

 property 

as the destination of a binding expression, as the following example shows:

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

    <MyComp:TextAreaFontControl id="myTA" 
        maxFontSize="{Number(myTI.text)}"/>

    <mx:Label text="Enter max font size."/>
    <mx:TextInput id="myTI" text="25"/>

</mx:Application>

In this example, any value that the user enters into the 

TextInput

 control is automatically 

copied to the 

maxFontSize

 property.

Using properties as the source of a data binding expression

When a property is the source of a data binding expression, Flex automatically copies the 
value of the source property to any destination property when the source property changes. 
However, in order to signal to Flex to perform the copy, you must register the property with 
Flex and the source property must dispatch an event. 

To register a property as a source for data bindings, you use the 

[Bindable]

 metadata tag. 

You can use this tag in three places:

■

Before a class definition to make all public properties defined as variables or by using setter 
and getter methods usable as the source of a binding expression

■

Before a property that a variable defines to make that specific property support binding

■

Before a getter method for a property implemented by using setter and getter methods

For more information on the 

[Bindable]

 metadata tag, see 

. 

NO

TE

When you use the 

[Bindable]

 metadata tag before a public class definition, it only 

applies to public properties; it does not apply to private or protected properties, or to 
properties defined in any other namespace. You must insert the 

[Bindable]

 metadata 

tag before a nonpublic property to make it usable as the source for a data binding 
expression.