MXML Components and ActionScript Classes

Question

Hello,
I am fairly new to Flex and OOP and am confused on how some parts of OOP work.
I have a Spark TextInput Component with an id which equals "test".
I also have a function that takes "test.text", appends a string to and and puts the resulting value into another TestInput called test2.
How can I move the "appendPhrase()" function into a class so that it would still accept values from "test" and change the "text2" values?
I tried creating a function that would assign the value of the varaible in the class using classname.variable name, made it bindable, and assigned
the text value of the textinput that value, but I was wondering if there was any other way I could do that?
~~~~~~~~~~~~~~~~Version1~~~~~~~~~~~~~~~~~~~~~
<fx:Script>
    private function appendPhrase():void
        test2.text = test.text + " was added";
</fx:Script>
<s:TextInput x="0" y="0" id="test" />
<s:TextInput x="0" y="10" id="test2" />
<s:Button click="appendPhrase();" />
~~~~~~~~~~~~~~~~~~Version 2:~~~~~~~~~~~~~~~~~
function in class:
public class ChangeString
    [Bindable]
    public var text:String;
    private function appendPhrase(firstString:Object):void
       text = firstString.text + " was added";
main.mxml:
[Bindable]
public var changed:Object = new ChangeString();
<s:TextInput x="0" y="0" id="test" click="changeValue(test.text)" />
<s:TextInput x="0" y="10" id="test2" text="{changed.text}"/>

Answer 1

package models
          [Bindable]
          public class MyViewModel
                    public var text:String "Hello ";
                    public function appendText(t:String):String
                              this.text = this.text + t;
                              return this.text;
<fx:Script>
<![CDATA[
import models.MyViewModel;
[Bindable]
public var model:MyViewModel = new MyViewModel();
]]>
</fx:Script>
<s:TextInput id="test" x="0" y="0" click="this.model.appendText(this.test.text)" text="World" />
<s:TextInput id="test2" x="0" y="10" text="{this.model.text}" />
I would go about it a little differently maybe. I would use the model class as a data holder, and use a private local method, utility class, or controller class to modify values on the model (data holder class).