"""http://code.activestate.com/recipes/131499-observer-pattern/""" 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()
点击run it 运行之!!!