metapie/events.py

   1 ############################################################################
   2 #   Copyright (C) 2005 by Reithinger GmbH
   3 #   mreithinger@web.de
   4 #
   5 #   This file is part of metapie.
   6 #
   7 #   metapie is free software; you can redistribute it and/or modify
   8 #   it under the terms of the GNU General Public License as published by
   9 #   the Free Software Foundation; either version 2 of the License, or
  10 #   (at your option) any later version.
  11 #
  12 #   pyplan is distributed in the hope that it will be useful,
  13 #   but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 #   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 #   GNU General Public License for more details.
  16 #
  17 #   You should have received a copy of the GNU General Public License
  18 #   along with this program; if not, write to the
  19 #   Free Software Foundation, Inc.,
  20 #   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  21 ############################################################################
  22
  23 import weakref
  24 try:
  25     set
  26 except NameError:
  27     from sets import Set as set
  28
  29
  30 class Subject(object):
  31     #no __init__ because auf ZODB
  32     #Subjects attributes are transient
  33     #and must be created on the flow
  34
  35     def detach_all(self):
  36         try:
  37             del self._v_observers
  38         except AttributeError: pass
  39
  40
  41     def attach(self, callback, event="default"):
  42         try:
  43             observers = self._v_observers
  44         except AttributeError:
  45             observers = self._v_observers = { }
  46
  47         ol = observers.get(event)
  48         if not ol: ol = observers[event] = set()
  49         ol.add(callback)
  50
  51
  52     def attach_weak(self, callback, event="default"):
  53         self.attach(weakref.ref(callback, self.__detach_weak), event)
  54
  55
  56     def __detach_weak(self, callback):
  57         self.detach(callback)
  58
  59
  60     def detach(self, callback=None, event=None):
  61         try:
  62             observers = self._v_observers
  63         except AttributeError:
  64             observers = self._v_observers = { }
  65
  66         if callback is None: observers.clear()
  67
  68         def detach_event(ol, callback):
  69             try:
  70                 if ol: ol.remove(callback)
  71             except KeyError:
  72                 pass
  73
  74         if event:
  75             detach_event(observers.get(event), callback)
  76         else:
  77             for ol in observers.itervalues():
  78                 detach_event(ol, callback)
  79
  80
  81
  82     def fire(self, event="default", *args, **kwargs):
  83         try:
  84             observers = self._v_observers
  85         except AttributeError:
  86             return
  87
  88         try:
  89             if self._v_events_disabled: return
  90         except AttributeError:
  91             pass
  92
  93         for cb in self._v_observers.get(event, ()):
  94             if type(cb) == weakref.ReferenceType:
  95                 cb = cb()
  96                 if cb: cb(*args, **kwargs)
  97             else:
  98                 cb(*args, **kwargs)
  99
 100
 101     def disable_events():
 102         try:
 103             self._v_events_disabled += 1
 104         except AttributeError:
 105             self._v_events_disabled = 1
 106
 107
 108     def enable_events():
 109         self._v_events_disabled -= 1
 110
 111
 112 if __name__ == "__main__":
 113     def test():
 114         sender = Subject()
 115
 116         def call_me():
 117             print "call me"
 118
 119         print "before attach"
 120         sender.attach_weak(call_me)
 121
 122         print "after attach"
 123
 124         sender.fire()
 125
 126         print "end"
 127
 128
 129     test()