cola/observable.py

   1 """The Observable class for decoupled notifications"""
   2 from __future__ import absolute_import, division, print_function, unicode_literals
   3
   4
   5 class Observable(object):
   6     """Handles subject/observer notifications."""
   7
   8     def __init__(self):
   9         self.notification_enabled = True
  10         self.observers = {}
  11
  12     def add_observer(self, message, observer):
  13         """Add an observer for a specific message."""
  14         observers = self.observers.setdefault(message, set())
  15         observers.add(observer)
  16
  17     def remove_observer(self, observer):
  18         """Remove an observer."""
  19         for _, observers in self.observers.items():
  20             if observer in observers:
  21                 observers.remove(observer)
  22
  23     def notify_observers(self, message, *args, **opts):
  24         """Pythonic signals and slots."""
  25         if not self.notification_enabled:
  26             return
  27         # observers can remove themselves during their callback so grab a copy
  28         observers = set(self.observers.get(message, set()))
  29         for method in observers:
  30             method(*args, **opts)