URLLoader and Loader classes

Have you ever had mystery errors that your content stopped working without a reason? Possibly you haven’t registered all important listeners, most examples are simplified, i.e.

var image:Loader = new Loader();
image.addeventListener(Event.COMPLETE, onImageLoaded);
image.load(new URLRequest("myImage.jpg"));

and this is fine as long:
– file exist
– your flash can access this resource
– you have debug version of flash player (it doesn’t stop error but it throws them in your face:) )

basically you should get a habit of listening for ALL important events: IOErrorEvent.IO_ERROR and SecurityErrorEvent.SECURITY_ERROR, those two are really important and will save you a lot of trouble. So revised example will look like follows:

var image:Loader = new Loader();
image.addeventListener(IOErrorEvent.IO_ERROR, onImageError, false, 0, true);
image.addeventListener(SecurityErrorEvent.SECURITY_ERROR, onImageError, false, 0, true);
image.addeventListener(Event.COMPLETE, onImageLoaded, false, 0, true);
image.load(new URLRequest("myImage.jpg"));

//somwhere later
function onImageError(e:Event):void
{
    //do something with the error, log it handle it (fall-back image) etc.
}

happy coding
p.s. title says about Loader and URLLoader as most frequently used but it is applicable to any Class that access external resource.