cola/observable.py

   1 # Copyright (C) 2007-2018 David Aguilar and contributors
   2 """This module provides the Observable class"""
   3 from __future__ import division, absolute_import, unicode_literals
   4
   5
   6 class Observable(object):
   7     """Handles subject/observer notifications."""
   8
   9     def __init__(self):
  10         self.notification_enabled = True
  11         self.observers = {}
  12
  13     def add_observer(self, message, observer):
  14         """Add an observer for a specific message."""
  15         observers = self.observers.setdefault(message, set())
  16         observers.add(observer)
  17
  18     def remove_observer(self, observer):
  19         """Remove an observer."""
  20         for _, observers in self.observers.items():
  21             if observer in observers:
  22                 observers.remove(observer)
  23
  24     def notify_observers(self, message, *args, **opts):
  25         """Pythonic signals and slots."""
  26         if not self.notification_enabled:
  27             return
  28         # observers can remove themselves during their callback so grab a copy
  29         observers = set(self.observers.get(message, set()))
  30         for method in observers:
  31             method(*args, **opts)