event handler advice

[sblakey at freei.com.bbs]

On Mon, Jul 17, 2000 at 03:49:02PM -0700, Pete Shinners wrote:
> i'm trying to write a simple event handler python class.
> so far i haven't come up with an 'elegant' solution i was
> expecting.
>
    <<snipped by Sean Blakey>>
>
> my guess is i need some dictionary that defines the
> messages and their routine name (no shortcut way to do
> this unless python had #define like macros :])
>
> messages = {msg.INIT:"INIT", msg.PLAY:"PLAY", ...etc}
>
> then a routine like
>
> class basehandler:
>     def handle(messageid):
>         name = messages[messageid]
>         self.name()   #HAHA, no really, how do i do this?
>
> but i'm not exactly sure how to write this. need help, thx
>
>
>
Probably he simplest solution is along the lines of:

class basehandler:
    def handle(messageid):
        name = messages[messageid]
        bound_method = getattr(self, name)
        bound_method()

Personally, I would be more comfortable with:

class basehandler:
    def handle(messageid):
        try:
            name = messages[messageid]
            bound_method = getattr(self, name)
        except KeyError:
            if __debug__: print 'Invalid message sent', messageid
            # or other error handling (syslog?)
        except AttributeError:
            if __debug__: print 'Unhandled message received', name
            # other misc error handling
        else:
            bound_method()

This approach allows trapping of "illegitimate" messages (or messages you
haven't gotten around to implementing yet) without the nastiness of an unhandles
exception.
        -Sean

--
Sean Blakey, sblakey at freei.com
Software Developer, FreeInternet.com
(253)796-6500x1025
"It ain't so much the things we don't know that get us in trouble.  It's the
things we know that ain't so."
-- Artemus Ward aka Charles Farrar Brown