How to manually trigger the click event in mxml?

I'm doing it this way :

<?xml version="1.0" encoding="utf-8"?>
<mx:Application initialize="onLoad()".开发者_StackOverflow社区..>
<mx:Button id="connect_btn" />  
<mx:Script>  
<![CDATA[   
      public function onLoad():void 
      { 
         connect_btn.click();
      } 
      ]]>  
</mx:Script>  
</mx:Application>

But get an error that connect_btn is not defined...

UPDATE

Yeah I'm trying to simulate a click event .

you can dispatch it like so:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application initialize="onLoad()"...>
<mx:Button id="connect_btn" />  
<mx:Script>  
<![CDATA[   
      public function onLoad():void 
      { 
         var e:MouseEvent = new MouseEvent(MouseEvent.CLICK);
         connect_btn.dispatchEvent(e);
      } 
      ]]>  
</mx:Script>  
</mx:Application>