Basics of exception handling
Exceptions are objects that are thrown
in the event of some exceptional (or unexpected) condition or error
and are used to describe the condition or error encountered. Standard
errors, such as null object references and division by zero, are
typically thrown by the runtime system. These types of errors could occur
anywhere in an application and you can include catch clauses
in any executable script to try to recover from these errors.
User-defined exceptions
There are also exceptional conditions that do not immediately
result in runtime errors. These exceptions typically occur during
execution of a function or a user-event script. To signal these
exceptions, you create user objects that inherit from the PowerScript
Exception class. You can associate a user-defined exception with
a function or user event in the prototype for the method.
For example, a user-defined exception might be created to
indicate that a file cannot be found. You could declare this exception
in the prototype for a function that is supposed to open the file.
To catch this condition, you must instantiate the user-defined exception
object and then throw the exception instance
in the method script.