List classes

Due to limitations in implementation, the scripting API is unable to return an array of sessions, users, certificates, or AltText objects. Instead, it returns a helper object of the corresponding list class, that is, SessionList, UserList, CertificateList, or AltTextList respectively.

These helper classes offer functions to access the items in the list, identical to the functions offered by the list classes in the flow element module (JobList etc).

Implementation note on Exceptions

The scripting API does not throw exceptions. All C++ toolkit exceptions must be caught within each scripting API function. In some cases the scripting API function description may describe what to do if an exception is caught (for example, return a null object). In many other cases, the scripting API states that the result is undefined or there simply is no described (or obvious) behavior. The recommended exception handling is as follows:

Issue an error message to the Switch message log, describing as clearly as possible what the problem is and what caused it.
Provide stable behavior, even if the requested function cannot be executed. For example, when writing to a read-only object, do nothing at all other than issuing an error message.
Avoid performing an operation partially; try to execute every operation completely or not at all.