Uploading Files using FileReference - Page 4

Errors and Error Handling:
We now need to deal with errors that may be generated from the application we were coding on the previous page. Since this application depends largely on a remote server, errors are somewhat harder to predict. Thankfully, most of them can be dealt with, and Flash can report what sorts of errors are occurring.

One of the more common errors is a permission error. Your server may allow an upload, but the script that you used to upload the file may not have permission to store that file in a directory on the server. Unfortunately, this sort of error isn't passed on to Flash, so test your upload script thoroughly before deploying it anywhere. Using Apache, this sort of error can be solved by changing the chmod of the folder to allow 'Other' the permission to write (I used 757). Similar permission settings can be changed using on a Windows server through IIS.

Note:

A little over a year ago, the previous change was the only one that I had to make. Several server configuration changes later, I noticed that file uploads weren't working any longer. Thanks to a note on the Adobe LiveDocs, I was able to fix the issue by adding the following lines to my .htaccess file:

SecFilterEngine Off
SecFilterScanPOST Off

Beware, the completion event fires before this error is thrown, so be sure that your code can handle such an error.

The error handling in this tutorial is contained within a single function. It would be possible to handle each of the three types of errors separately, but the error response in this case will be so similar for each type that they group logically into one function:

function handleError(errorName:String, detail:Object):Void {

restart();

if (arguments.length === 2) {

if (typeof detail === 'number') {

display_txt.text = 'HTTP Error #'+detail;

} else {

display_txt.text = 'Security Error: '+detail;

}

} else {

display_txt.text = 'IO Error';

}

}

The application resets itself when an error occurs, just as it did when it completed successfully. This way, the user can try again and hopefully avoid the error. The conditional statements following the restart check the type of error. Conveniently, the three kinds of errors all pass slightly different arguments into the handler. An IOError only passes one argument, so it is easily identified by checking the length of the arguments array accessible from every function. HTTP and IO errors both pass two arguments, but an HTTPError passes the second argument as a Number, not a String. This difference can be detected using the typeof operator. In any case, the application simply passes along all of the information it is given to the user.

Wrap Up:
Hopefully this tutorial has served as a useful introduction to the upload features of the FileReference class. As always, the kForums are available for questions, and I always try to respond to my PMs (though the forums are usually a more effective means of getting help).

Krilnon Reclipse

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