When you publish a FLA document, Flash "compiles" it into a SWF movie. The compiling process organizes and converts document assets into finished, usable media for the Flash player (and Lassie). However, the Flash compiler may encounter configuration errors while running, at which to it aborts the compile process and throws an error. Errors will appear in the Flash Output window (which will automatically pop-open when an error is encountered). Compiler errors must be resolved before the document can publish and its resulting SWF can be used by Lassie.
So, first thing first: if you encounter a compiler error, don't panic. It's not the end of the world. The compiler exists because we are all human and we make mistakes. Compiler errors are designed to be our friend and help us work through those mistakes. And while the Flash compiler can be annoyingly picky, it is also extremely helpful with how specific it is about errors.
It is important to be aware that any custom ActionScript that you write into the Flash media within your library is also subject to the rigorous scrutiny of the Flash compiler. So, if you've followed this tutorial to the letter and still get compiler errors, there's a very good chance that it's being cause by your own scripts within the library. At which time - good luck. You're on your own.
To avoid uncertainty surrounding the source of an error, it's a good idea to develop your own custom scripts in a separate FLA document where you can publish and test them on their own. Once your own scripted media is working and error-free, move it over into your Lassie library document. This will isolate your own script errors from ones that may be encountered while setting up your library document.
Assuming that you can rule out your own scripts as a source of compiler errors, then there are only a couple errors that you are likely to encounter while following this tutorial. They include:
1120: Access of undefined property [name].Check your class declarations list on frame-1. The compiler is telling you that it can't find a class that you've referenced, which probably means that you've mistyped a class name in the list. Look at the [name] portion of the error message to see your specified class name that Flash could not find.
1151: A conflict exists with definition [name] in namespace internal.
Check your class declarations list on frame-1. This message probably means that you've declared the same class multiple times in the list. See the [name] portion of the message for reference as to which class name is in question.
You may encounter situations when your library SWF successfully compiles without errors, but not all of its class assets are available in the Lassie Engine. Or in a worst-case scenarios, the library may be completely unavailable within Lassie. Don't panic. If the library compiled, then the error is most likely just a simple configuration issue. The following covers common configuration issues.
Did you compile the updated FLA into a SWF? (File > Publish). If so, has the new SWF replaced the old SWF library at the location Lassie is reading it from... ie: have you uploaded the updated movie to your Lassie development site? If so, have you emptied your browser's cache and refreshed the page?
Look over your list of class declarations in the library's frame-1 actions. Did you forget to declare the class? A classified asset will not be available within Lassie until it has been declared in that list.
Check your document class path (Properties Panel > Document Class). Does your document class match what is specified in step-2 of this tutorial? If so, click the little pencil button next to the Document Class field. If a script file pops open, that's good (just close the script without editing). If an alert pops open, however, it probably contains the message: "A definition for the document class could not be found...". If you encounter this message, it means that your document is not linked correctly to the AssetLibrary script file. Review steps 1 and 2 of this tutorial on how to correctly organize your production files so that all links work.