'''
Created on 2013-10-22
@author: Administrator
'''
class Subject(object):
def __init__(self):
self._observers=[]
def attach(self,observer):
if not observer in self._observers:
self._observers.append(observer)
def detach(self,observer):
try:
self._observers.remove(observer)
except ValueError:
pass
def notify(self,modifier=None):
for observer in self._observers:
if modifier!=observer:
observer.update(self)
#example usage
class Data(Subject):
def __init__(self,name=''):
Subject.__init__(self)
self.name=name
self.data=0
@property
def data(self):
return self._data
@data.setter
def data(self,value):
self._data=value
self.notify()
class HexViewer:
def update(self,subject):
print('HexViewer: Subject %s has data 0x%x' %
(subject.name, subject.data))
class DecimalViewer:
def update(self,subject):
print('DecimalViewer: subject %s has data %d' %(subject.name,subject.data))
#example usage
def main():
data1=Data('Data 1')
data2=Data('Data 2')
view1=DecimalViewer()
view2=HexViewer()
data1.attach(view1)
data1.attach(view2)
data2.attach(view2)
data2.attach(view1)
print("Setting Data 1 = 10")
data1.data = 10
print("Setting Data 2 = 15")
data2.data = 15
print("Setting Data 1 = 3")
data1.data = 3
print("Setting Data 2 = 5")
data2.data = 5
print("Detach HexViewer from data1 and data2.")
data1.detach(view2)
data2.detach(view2)
print("Setting Data 1 = 10")
data1.data = 10
print("Setting Data 2 = 15")
data2.data = 15
if __name__ == '__main__':
main()
