cola/observable.py

   1 # Copyright (c) 2008 David Aguilar
   2 """This module provides the Observable class"""
   3
   4 import types
   5
   6 class Observable(object):
   7     """Handles subject/observer notifications."""
   8     def __init__(self):
   9         self.observers = set()
  10         self.message_observers = {}
  11         self.notification_enabled = True
  12
  13     def add_observer(self, observer):
  14         """Adds an observer to this model"""
  15         self.observers.add(observer)
  16
  17     def add_message_observer(self, message, observer):
  18         """Add an observer for a specific message."""
  19         observers = self.message_observers.setdefault(message, set())
  20         observers.add(observer)
  21
  22     def remove_observer(self, observer):
  23         """Remove an observer."""
  24         if observer in self.observers:
  25             self.observers.remove(observer)
  26         for message, observers in self.message_observers.items():
  27             if observer in observers:
  28                 observers.remove(observer)
  29
  30     def notify_observers(self, *param):
  31         """Notifies observers about attribute changes"""
  32         if not self.notification_enabled:
  33             return
  34         for observer in self.observers:
  35             observer.notify(*param)
  36
  37     def notify_message_observers(self, message, *args, **opts):
  38         """Pythonic signals and slots."""
  39         if not self.notification_enabled:
  40             return
  41         observers = self.message_observers.get(message, ())
  42         for method in observers:
  43             method(*args, **opts)