tests/pyatspi/pasytest/Events.py

   1 #C#-Style Events in Python
   2 #Taken from http://code.activestate.com/recipes/410686/
   3 #By Zoran Isailovski
   4
   5 class Events:
   6         def __getattr__(self, name):
   7                 if hasattr(self.__class__, '__events__'):
   8                         assert name in self.__class__.__events__, \
   9                                          "Event '%s' is not declared" % name
  10                 self.__dict__[name] = ev = _EventSlot(name)
  11                 return ev
  12         def __repr__(self): return 'Events' + str(list(self))
  13         __str__ = __repr__
  14         def __len__(self): return NotImplemented
  15         def __iter__(self):
  16                 def gen(dictitems=self.__dict__.items()):
  17                         for attr, val in dictitems:
  18                                 if isinstance(val, _EventSlot):
  19                                         yield val
  20                 return gen()
  21
  22 #------------------------------------------------------------------------------
  23
  24 class _EventSlot:
  25         def __init__(self, name):
  26                 self.targets = []
  27                 self.__name__ = name
  28         def __repr__(self):
  29                 return 'event ' + self.__name__
  30         def __call__(self, *a, **kw):
  31                 for f in self.targets: f(*a, **kw)
  32         def __iadd__(self, f):
  33                 self.targets.append(f)
  34                 return self
  35         def __isub__(self, f):
  36                 while f in self.targets: self.targets.remove(f)
  37                 return self
  38
  39 #------------------------------------------------------------------------------
  40
  41 if __name__ == '__main__':
  42
  43         class MyEvents(Events):
  44                 __events__ = ('OnChange', )
  45
  46         class ValueModel(object):
  47                 def __init__(self):
  48                         self.events = MyEvents()
  49                         self.__value = None
  50                 def __set(self, value):
  51                         if (self.__value == value): return
  52                         self.__value = value
  53                         self.events.OnChange()
  54                         ##self.events.OnChange2() # would fail
  55                 def __get(self):
  56                         return self.__value
  57                 Value = property(__get, __set, None, 'The actual value')
  58
  59         class SillyView(object):
  60                 def __init__(self, model):
  61                         self.model = model
  62                         model.events.OnChange += self.DisplayValue
  63                         ##model.events.OnChange2 += self.DisplayValue # would raise exeception
  64                 def DisplayValue(self):
  65                         print self.model.Value
  66
  67
  68         model = ValueModel()
  69         view = SillyView(model)
  70
  71         print '\n--- Events Demo ---'
  72         # Events in action
  73         for i in range(5):
  74                 model.Value = 2*i + 1
  75         # Events introspection
  76         print model.events
  77         for event in model.events:
  78                 print event