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Arevos · Feb 23rd, 2006, 5:59 PM

Multimethods spring to mind as one good use for decorators, and since a while ago we were talking about thread, here's a decorator that mimics the synchronized keyword in Java. I also find decorators quite useful for event based programming:

(Toggle Plain Text)

event_registry = {}

def listen_for(event_class):
    if event_registry.has_key(event_class):
        event_registry[event_class].append(func)
    else:
        event_registry[event_class] = [func]

    def decorator(func):
        def decorated(event):
            return func(event)
        return decorated
    return decorator

def send_event(event):
    if event_registry.has_key(event.__class__):
        for func in event_registry[event.__class__]:
            func(event)

class PokeEvent: pass

@listen_for(PokeEvent)
def poked(event):
    print "Ouch!"

send_event(PokeEvent())

Although I'd probably opt for an off-the-shelf dispatch system, rather than trying to reinvent the wheel, if I were programming a real application.

Feb 23rd, 2006, 5:59 PM	#5
Arevos Programming Guru Join Date: Aug 2005 Location: England Posts: 1,499 Rep Power: 5	Multimethods spring to mind as one good use for decorators, and since a while ago we were talking about thread, here's a decorator that mimics the synchronized keyword in Java. I also find decorators quite useful for event based programming: (Toggle Plain Text) event_registry = {} def listen_for(event_class): if event_registry.has_key(event_class): event_registry[event_class].append(func) else: event_registry[event_class] = [func] def decorator(func): def decorated(event): return func(event) return decorated return decorator def send_event(event): if event_registry.has_key(event.__class__): for func in event_registry[event.__class__]: func(event) class PokeEvent: pass @listen_for(PokeEvent) def poked(event): print "Ouch!" send_event(PokeEvent()) event_registry = {} def listen_for(event_class): if event_registry.has_key(event_class): event_registry[event_class].append(func) else: event_registry[event_class] = [func] def decorator(func): def decorated(event): return func(event) return decorated return decorator def send_event(event): if event_registry.has_key(event.__class__): for func in event_registry[event.__class__]: func(event) class PokeEvent: pass @listen_for(PokeEvent) def poked(event): print "Ouch!" send_event(PokeEvent()) Although I'd probably opt for an off-the-shelf dispatch system, rather than trying to reinvent the wheel, if I were programming a real application.