ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Handling errors
public class AppError extends Error
{
public function AppError(message:String, errorID:int)
{
super(message, errorID);
}
}
The following shows an example of using AppError in your project:
try
{
throw new AppError("Encountered Custom AppError", 29);
}
catch (error:AppError)
{
trace(error.errorID + ": " + error.message)
}
Note: If you want to override the Error.toString() method in your subclass, give it one ...(rest) parameter. The
ECMAScript language specification on which ActionScript 3.0 is based defines the Error.toString() method that way,
and ActionScript 3.0 defines it the same way for backward compatibility. Therefore, when you override the
Error.toString() method, match the parameters exactly. You do not want to pass any parameters to your
toString() method at runtime, because those parameters are ignored.
Responding to error events and status
Flash Player 9 and later, Adobe AIR 1.0 and later
One of the most noticeable improvements to error handling in ActionScript 3.0 is the support for error event handling
for responding to asynchronous errors while an application is running. (For a definition of asynchronous errors, see
“Types of errors” on page 53.)
You can create event listeners and event handlers to respond to the error events. Many classes dispatch error events
the same way they dispatch other events. For example, an instance of the XMLSocket class normally dispatches three
types of events: Event.CLOSE, Event.CONNECT, and DataEvent.DATA. However, when a problem occurs, the
XMLSocket class can dispatch the IOErrorEvent.IOError or the SecurityErrorEvent.SECURITY_ERROR. For
more information about event listeners and event handlers, see “Handling events” on page 125.
Error events fit into one of two categories:
Error events that extend the ErrorEvent class
The flash.events.ErrorEvent class contains the properties and methods for managing errors related to networking
and communication operations in a running application. The AsyncErrorEvent, IOErrorEvent, and
SecurityErrorEvent classes extend the ErrorEvent class. If you’re using the debugger version of a Flash runtime, a
dialog box informs you at run-time of any error events without listener functions that the player encounters.
Status-based error events
The status-based error events are related to the netStatus and status properties of the networking and
communication classes. If a Flash runtime encounters a problem when reading or writing data, the value of the
netStatus.info.level or status.level properties (depending on the class object you’re using) is set to the
value "error". You respond to this error by checking if the level property contains the value "error" in your
event handler function.
Last updated 6/6/2012
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