If you want code to be able to handle your signalled exceptions, you will
probably want to provide a way to pick those kinds out automatically.
The easiest way to do this is to subclass
First, you should choose an exception class to specialize.
is the best choice for non-resumable exceptions, and
or its subclass
Warning is best for exceptions that should resume
nil by default.
Exceptions are just normal objects; include whatever information you think
would be useful to handlers. Note that there are two textual description
fields, a description and a message text. The description,
if provided, should be a more-or-less constant string answered from a
override method on
#description, meant to describe all instances
of your exception class. The message text is meant to be provided at
the point of signalling, and should be used for any extra information
that code might want to provide. Your signalling code can provide the
messageText by using
#signal: instead of
This is yet another reason why signalling variants of instance creation
messages can be more trouble than they’re worth.