ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Handling errors
There are different ways you can approach error handling in your application. The following list summarizes the three
major options for handling errors:
Use try..catch..finally statements. These statements catch synchronous errors as they occur. You can nest
your statements into a hierarchy to catch exceptions at various levels of code execution. For more information, see
“Using try..catch..finally statements” on page 58.
Create your own custom error objects. You can use the Error class to create your own custom error objects to track
specific operations in your application that are not covered by built-in error types. Then you can use
try..catch..finally statements on your custom error objects. For more information see “Creating custom
error classes” on page 62.
Write event listeners and handlers to respond to error events. By using this strategy, you can create global error
handlers that let you handle similar events without duplicating much code in try..catch..finally blocks. You
are also more likely to catch asynchronous errors using this approach. For more information, see “Responding to
error events and status” on page 63.
Working with the debugger versions of Flash runtimes
Flash Player 9 and later, Adobe AIR 1.0 and later
Adobe provides developers with special editions of the Flash runtimes to assist debugging efforts. You obtain a copy
of the debugger version of Flash Player when you install Adobe Flash Professional or Adobe Flash Builder. You also
obtain a utility for the debugging of Adobe AIR applications, which is called ADL, when you install either of those
tools, or as part of the Adobe AIR SDK.
There is a notable difference in how the debugger versions and the release versions of Flash Player and Adobe AIR
indicate errors. The debugger versions shows the error type (such as a generic Error, IOError, or EOFError), error
number, and a human-readable error message. The release versions shows only the error type and error number. For
example, consider the following code:
try
{
tf.text = myByteArray.readBoolean();
}
catch (error:EOFError)
{
tf.text = error.toString();
}
If the readBoolean() method throws an EOFError in the debugger version of Flash Player, the following message
displays in the tf text field: “EOFError: Error #2030: End of file was encountered.”
The same code in a release version of Flash Player or Adobe AIR would display the following text: “EOFError: Error
#2030.”
Note: The debugger players broadcast an event named "allComplete"; avoid creating custom events with the name
“allComplete”. Otherwise, you will encounter unpredictable behavior when debugging.
To keep resources and size to a minimum in the release versions, error message strings are not present. You can look
up the error number in the documentation (the appendixes of the ActionScript 3.0 Reference for the Adobe Flash
Platform) to correlate to an error message. Alternatively, you can reproduce the error using the debugger versions of
Flash Player and AIR to see the full message.
Last updated 6/6/2012
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