User Guide

Handling errors for a Connection object 171
Error-handling strategies
Flash applications use error-handling code less often than server applications do, because Flash
does not report errors to the user when the user is viewing SWF files. However, Flash Remoting
does make error information available to the Flash SWF ActionScript, and your application can
use this information. The error-handling hierarchy lets you handle errors with any degree of
granularity. For example:
• You can use a global error handler to log error information if the status event cannot be
otherwise handled.
• You can display a message to the user in response to specific functions or in response to specific
errors returned by specific functions.
Error handling can be particularly useful for remote services, because the user’s experience
depends on remote data that might not always be retrieved, and it might not be obvious that data
is not retrieved. Also, in some cases, the error-handling code can even recover from a transient
error. For example, if a service function fails due to a time-out, it might be appropriate for the
Flash application to try the request a second time. If the request fails a second time, the SWF file
could then display a message to the user and post a message to the server to log the error.
The following example adds error handling to the example presented in “Directing results for a
service to specific responder objects” on page 168. The error handlers for the
helloWorld() and
what() service function calls display custom messages to the user. The general error handler
displays a generalized message.
import mx.remoting.NetServices;
import mx.remoting.Connection;
// initialization code specifies gateway, creates connection, calls service
if (inited == null)
{
inited = true;
NetServices.setDefaultGatewayUrl("http://localhost:8300/flashservices/
gateway")
var gatewayConnection:Connection = NetServices.createGatewayConnection();
// specify this object (this) as the responder object
howdyService =
gatewayConnection.getService("remoteservices");
}
// function specific result handler objects
function helloWorld_Result()
{
this.onResult = function(result){
// display successful result
messageDisplay.text = result;
}
this.onStatus = function(error){
// display successful result
messageDisplay.text = error.description;
}
}
function whatsUp_Result()
{