ugit/observer.py

   1 #!/usr/bin/env python
   2 from pprint import pformat
   3
   4 class Observer(object):
   5         '''Observers receive notify(*attributes) messages from their
   6         subjects whenever new data arrives.  This notify() message signifies
   7         that an observer should update its internal state/view.'''
   8
   9         def __init__(self, model):
  10                 self.model = model
  11                 self.model.add_observer(self)
  12                 self.__debug = False
  13
  14         def __del__(self):
  15                 self.model.remove_observer(self)
  16
  17         def set_debug(self, enabled):
  18                 self.__debug = enabled
  19
  20         def notify(self, *attributes):
  21                 '''Called by the model to notify Observers about changes.'''
  22                 # We can be notified about multiple attribute changes at once
  23                 model = self.model
  24                 for attr in attributes:
  25                         notify = model.get_notify()
  26                         model.set_notify(False) # NOTIFY OFF
  27
  28                         value = model.get_param(attr)
  29                         self.subject_changed(attr, value)
  30
  31                         model.set_notify(notify) # NOTIFY ON
  32
  33         def subject_changed(self, attr, value):
  34                 '''This method handles updating of the observer/UI.
  35                 This must be implemented in each concrete observer class.'''
  36
  37                 msg = 'Concrete Observers must override subject_changed().'
  38                 raise NotImplementedError, msg