root/gaphor/tags/gaphor-0.12.5/gaphor/misc/signal.py

# vim: sw=4

import types

__version__ = "$Revision$"
__author__ = "Arjan Molenaar"
__date__ = "2002-08-28"

class Signal:
    """The signal class is an implementation of the Observer pattern.

    It can be used to send signals to every function or method that connected
    to the signal object, with a variable amount of parameters. Note that the
    owner of the Signal instance should define a protocol for notifying the
    observers.  The subject should provide methods for connecting and
    disconnecting observers (preferably 'connect()' and 'disconnect()'.
    """

    def __init__(self):
        # Signals are stored in a list as [ (signal_func, (data)), <next sig> ]
        self.__signals = [ ]

#    def __signal_handler_destroyed(self, ref):
#        print '__signal_handler_destroyed'
#        self.__signals = filter (lambda o: o[0] != ref,
#                                 self.__signals)
        
    def connect (self, signal_handler, *data):
        """Connect to the object. You should provide a signal handler and a
        bunch of parameters that should be passed to the signal handler.
        """
        #print 'Signal.connect():', data
        self.__signals.append ((signal_handler,) + data)
        #self.__signals.append ((weakref.ref(signal_handler, self.__signal_handler_destroyed),) + data)

    def disconnect (self, signal_handler):
        """Disconnect the signal_handler (observer).
        """
        self.__signals = filter (lambda o: o[0] != signal_handler,
                                 self.__signals)

    def disconnect_by_data (self, *data):
        #print 'Signal::disconnect_by_data', len (self.__signals)
        self.__signals = filter (lambda o: o[1:] != data,
                                 self.__signals)
        #print 'Signal::disconnect_by_data', len (self.__signals)

    def emit (self, *keys):
        """Emit the signal. A set of parameters can be defined that will be
        passed to the signal handler. Those parameters will be set before
        the parameters provided through the connect() method.
        In case there are queued emisions, this function will queue the
        signal emision too.

        Note that you should define how many parameters are provided by the
        owner of the signal.
        """
        #print 'Signal.emit():', keys
        for signal in self.__signals:
            signal_handler = signal[0]
            data = keys + signal[1:]
            apply(signal_handler, data)