Restricting which characters a user can type in a Spark TextInput control in Flex 4

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/04/21/restricting-which-characters-a-user-can-type-in-a-spark-textinput-control-in-flex-gumbo/ -->
<s:Application name="Spark_TextInput_restrict_test"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark">
 
    <s:VGroup horizontalCenter="0" verticalCenter="0">
        <s:SimpleText text="Allowed characters are 0-9 and A-F:" />
        <s:TextInput id="textInput"
                restrict="0-9A-F"
                widthInChars="20"
                maxChars="20" />
    </s:VGroup>
 
</s:Application>

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2009/04/21/restricting-which-characters-a-user-can-type-in-a-spark-textinput-control-in-flex-gumbo/ -->
<s:Application name="Spark_TextInput_restrict_test"
        xmlns:fx="http://ns.adobe.com/mxml/2009"
        xmlns:s="library://ns.adobe.com/flex/spark"
        initialize="init();">
 
    <fx:Script>
        <![CDATA[
            import spark.primitives.SimpleText;
            import spark.components.VGroup;
            import spark.components.TextInput;
 
            private var vGroup:VGroup;
            private var simpleText:SimpleText;
            private var textInput:TextInput;
 
            private function init():void {
                simpleText = new SimpleText();
                simpleText.text = "Allowed characters are 0-9 and A-F:";
 
                textInput = new TextInput();
                textInput.restrict = "0-9A-F";
                textInput.widthInChars = 20;
                textInput.maxChars = 20;
 
                vGroup = new VGroup();
                vGroup.horizontalCenter = 0;
                vGroup.verticalCenter = 0;
                vGroup.addElement(simpleText);
                vGroup.addElement(textInput);
                addElement(vGroup);
            }
        ]]>
    </fx:Script>
 
</s:Application>