Macromedia flex 2 Manuale

210

Creating Custom Formatters

You can use this formatter in a Flex application, as the following example shows:

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

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" 
    xmlns:MyComp="myFormatters.*"> 

    <!-- Declare a formatter and specify formatting properties. -->
    <MyComp:SimpleFormatter id="upperFormat" myFormatString="upper" />

    <!-- Trigger the formatter while populating a string with data. -->
    <mx:TextInput id="myTI" /> 
    
    <mx:TextArea text="Your uppercase string is 
{upperFormat.format(myTI.text)}" />
 
</mx:Application>

The namespace declaration in the 

<mx:Application>

 tag specifies to use the 

MyComp

 prefix 

when referencing the formatter, and the location of the formatter’s ActionScript file. That file 
is in the myFormatters subdirectory of the application, or in the default classpath of the 
application. For more information on deploying your formatters, see 

Handling errors in formatters

For all formatter classes, except for the 

SwitchSymbolFormatter

 class, when an error occurs, 

the formatter returns an empty string and writes a string that describes the error condition to 
the formatter’s 

error

 property. The 

error

 property is inherited from the 

Formatter

 

superclass.

In your application, you can test for an empty string in the result returned by the formatter. If 
detected, you can check the 

error

 property to determine the cause of the error. For an 

example that handles a formatter error, see Chapter 41, “Formatting Data,” in Flex 2 
Developer’s Guide. For more information on the SwitchSymbolFormatter class, see