【设计模式】观察者模式(observer)c#/python实现

View Code 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=''):
super(Data,self).__init__()
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()