The Developer's Guide is wrong... you won't get a compilation error if
you don't cast. However, casting is best practice so that the compiler
can help you catch coding mistakes. For example,
e.currentTarget.setSytle(...)
would compile despite the typo, but throw a runtime error. However,
Button(e.currentTarget).setSytle(...)
would not compile.
- Gordon
________________________________
From: [email protected] [mailto:[EMAIL PROTECTED] On
Behalf Of Karl Johnson
Sent: Tuesday, February 27, 2007 10:27 AM
To: [email protected]; [email protected]
Subject: RE: [flexcoders] Basic inheritance question
In general you always want to cast something like this - because
event.currentTarget is of type object and NOT UIComponent or Button. But
since objects are loosely typed as type Object, then you reference any
property or method you want at compile time. Often at runtime though you
will hit errors unless it is properly casted. Your sample application
was done in Flex 2 right?
Definitely a best practice to be casting generic objects like this to
the type of object you want to be working with to avoid runtime errors
Karl
Cynergy
________________________________
From: [email protected] on behalf of jairokan
Sent: Tue 2/27/2007 11:53 AM
To: [email protected]
Subject: [flexcoders] Basic inheritance question
Hi,
I'm reading the Developer's Guide and in the section using Events, they
say on a paragraph that :
"If you try to call another method on the currentTarget (for example,
the setStyle() method), Flex returns an error. The setStyle() method is
defined on UIComponent, a subclass of DisplayObject. Therefore, you must
cast currentTarget to UIComponent before calling the setStyle() method"
for example:
<mx:Script>
<![CDATA[
import mx.core.UIComponent;
private function myEventHandler(e:Event):void {
UIComponent(e.currentTarget).setStyle("color", "red");
}
]]>
</mx:Script>
and e.currentTarget is of type Button. But Button extends UIComponent,
so we don't have to upcast the reference because setStyle method is
public and is available to Button object reference0. I tried the code
without upcasting and it works.
Is the writer wrong or Am I missing something on the concept.
Thanks
Jairo
