Question

I have a code in MXML and ActionScript that I found in a Flex manual. The problem is with “val” variable that should be passed to the updateMyString() function calling statement as a parameter but it doesn’t happen in the code. Why is that?

<?xml version="1.0"?>
<!-- binding/BindSetterAS.mxml -->
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
    xmlns:s="library://ns.adobe.com/flex/spark" 
    xmlns:mx="library://ns.adobe.com/flex/mx">
    <s:layout>
        <s:VerticalLayout/>
    </s:layout>
    <fx:Script>
        <![CDATA[
            import mx.binding.utils.*;
            import mx.events.FlexEvent;
            // Method called when myTI.text changes.
            public function updateMyString(val:String):void {
                myTA.text = val.toUpperCase();
            }
            <!-- Event listener to configure binding. -->
            public function mySetterBinding(event:FlexEvent):void {
                var watcherSetter:ChangeWatcher = 
                    BindingUtils.bindSetter(updateMyString, myTI, "text");
            }
        ]]>
    </fx:Script>
    <s:Label text="Bind Setter using setter method"/>
    <s:TextInput id="myTI" 
        text="Hello Setter" />
    <s:TextArea id="myTA" 
        initialize="mySetterBinding(event);"/>
</s:Application>

Answer 1

The documentation says that BindingUtils.bindSetter expects a setter function with one argument:

setter:Function — Setter method to invoke with an argument of the current value of chain when that value changes

In this case the val parameter will be set to the current value of chain. You can read about it here: http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/mx/binding/utils/BindingUtils.html#bindSetter

Hope this helps!