######################################################################
##
## Events
##
######################################################################
class Events:
def __getattr__(self, name):
if hasattr(self.__class__, '__events__'):
assert name in self.__class__.__events__, \
"Event '%s' is not declared" % name
self.__dict__[name] = ev = _EventSlot(name)
return ev
def __repr__(self): return 'Events' + str(list(self))
__str__ = __repr__
def __len__(self): return NotImplemented
def __iter__(self):
def gen(dictitems=self.__dict__.items()):
for attr, val in dictitems:
if isinstance(val, _EventSlot):
yield val
return gen()
class _EventSlot:
def __init__(self, name):
self.targets = []
self.__name__ = name
def __repr__(self):
return 'event ' + self.__name__
def __call__(self, *a, **kw):
for f in self.targets: f(*a, **kw)
def __iadd__(self, f):
self.targets.append(f)
return self
def __isub__(self, f):
while f in self.targets: self.targets.remove(f)
return self
######################################################################
##
## Demo
##
######################################################################
if __name__ == '__main__':
class MyEvents(Events):
__events__ = ('OnChange', )
class ValueModel(object):
def __init__(self):
self.events = MyEvents()
self.__value = None
def __set(self, value):
if (self.__value == value): return
self.__value = value
self.events.OnChange()
##self.events.OnChange2() # would fail
def __get(self):
return self.__value
Value = property(__get, __set, None, 'The actual value')
class SillyView(object):
def __init__(self, model):
self.model = model
model.events.OnChange += self.DisplayValue
##model.events.OnChange2 += self.DisplayValue # would raise exeception
def DisplayValue(self):
print self.model.Value
model = ValueModel()
view = SillyView(model)
print '\n--- Events Demo ---'
# Events in action
for i in range(5):
model.Value = 2*i + 1
# Events introspection
print model.events
for event in model.events:
print event
