cola/observable.py

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