"""
File: signals.py
Author: Patrick Chasco
Created: July 26, 2005
Purpose: A signals implementation
"""
#========================================================
# Implementation
#========================================================
from weakref import *
import inspect
class Signal:
"""
class Signal
A simple implementation of the Signal/Slot pattern. To use, simply
create a Signal instance. The instance may be a member of a class,
a global, or a local; it makes no difference what scope it resides
within. Connect slots to the signal using the "connect()" method.
The slot may be a member of a class or a simple function. If the
slot is a member of a class, Signal will automatically detect when
the method's class instance has been deleted and remove it from
its list of connected slots.
"""
def __init__(self):
self.slots = []
# for keeping references to _WeakMethod_FuncHost objects.
# If we didn't, then the weak references would die for
# non-method slots that we've created.
self.funchost = []
def __call__(self, *args, **kwargs):
for i in range(len(self.slots)):
slot = self.slots[i]
if slot != None:
slot(*args, **kwargs)
else:
del self.slots[i]
def call(self, *args, **kwargs):
self.__call__(*args, **kwargs)
def connect(self, slot):
self.disconnect(slot)
if inspect.ismethod(slot):
self.slots.append(WeakMethod(slot))
else:
o = _WeakMethod_FuncHost(slot)
self.slots.append(WeakMethod(o.func))
# we stick a copy in here just to keep the instance alive
self.funchost.append(o)
def disconnect(self, slot):
try:
for i in range(len(self.slots)):
wm = self.slots[i]
if inspect.ismethod(slot):
if wm.f == slot.im_func and wm.c() == slot.im_self:
del self.slots[i]
return
else:
if wm.c().hostedFunction == slot:
del self.slots[i]
return
except:
pass
def disconnectAll(self):
del self.slots
del self.funchost
self.slots = []
self.funchost = []
class _WeakMethod_FuncHost:
def __init__(self, func):
self.hostedFunction = func
def func(self, *args, **kwargs):
self.hostedFunction(*args, **kwargs)
# this class was generously donated by a poster on ASPN (aspn.activestate.com)
class WeakMethod:
def __init__(self, f):
self.f = f.im_func
self.c = ref(f.im_self)
def __call__(self, *args, **kwargs):
if self.c() == None : return
self.f(self.c(), *args, **kwargs)
#========================================================
# Example usage
#========================================================
if __name__ == "__main__":
class Button:
def __init__(self):
# Creating a signal as a member of a class
self.sigClick = Signal()
class Listener:
# a sample method that will be connected to the signal
def onClick(self):
print "onClick ", repr(self)
# a sample function to connect to the signal
def listenFunction():
print "listenFunction"
# a function that accepts arguments
def listenWithArgs(text):
print "listenWithArgs: ", text
b = Button()
l = Listener()
# Demonstrating connecting and calling signals
print
print "should see one message"
b.sigClick.connect(l.onClick)
b.sigClick()
# Disconnecting all signals
print
print "should see no messages"
b.sigClick.disconnectAll()
b.sigClick()
# connecting multiple functions to a signal
print
print "should see two messages"
l2 = Listener()
b.sigClick.connect(l.onClick)
b.sigClick.connect(l2.onClick)
b.sigClick()
# disconnecting individual functions
print
print "should see two messages"
b.sigClick.disconnect(l.onClick)
b.sigClick.connect(listenFunction)
b.sigClick()
# signals disconnecting automatically
print
print "should see one message"
b.sigClick.disconnectAll()
b.sigClick.connect(l.onClick)
b.sigClick.connect(l2.onClick)
del l2
b.sigClick()
# example with arguments and a local signal
print
print "should see one message"
sig = Signal()
sig.connect(listenWithArgs)
sig("Hello, World!")
