Python: Observer Pattern

 

GeovinDuObserver.py

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108

# 观察者模式  Observer Pattern # The Observer class that recieves updates from the ticker on a specific symbol: class TickerObserver(object):       def __init__(self, tickerSymbol):         self.tickerSymbol = tickerSymbol         self.lastPrice = 0.0       def Update(self, symbol, price):         if symbol == self.tickerSymbol:             self.lastPrice = price       def GetTicker(self):         return self.tickerSymbol + " : " + str(self.lastPrice)     # The ticker subject that sends out updates to all observers: class StockTicker(object):       def __init__(self):         self.observers = []       def AttachObserver(self, tickerObserver):         self.observers.append(tickerObserver)       def RemoveObserver(self, tickerObserver):         self.observers.remove(tickerObserver)       def Notify(self, symbol, price):         for observer in self.observers:             observer.Update(symbol, price)     class Subject:     """Represents what is being observed"""       def __init__(self):           """create an empty observer list"""           self._observers = []       def notify(self, modifier=None):           """Alert the observers"""           for observer in self._observers:             if modifier != observer:                 observer.update(self)       def attach(self, observer):           """If the observer is not in the list,         append it into the list"""           if observer not in self._observers:             self._observers.append(observer)       def detach(self, observer):           """Remove the observer from the observer list"""           try:             self._observers.remove(observer)         except ValueError:             pass     class Data(Subject):     """monitor the object"""       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:     """updates the Hexviewer"""       def update(self, subject):         print('HexViewer十六进制查看器: 实验对象 {} 转换的数据为： 0x{:x}'.format(subject.name, subject.data))     class OctalViewer:     """updates the Octal viewer"""       def update(self, subject):         print('OctalViewer八进制查看器: 实验对象' + str(subject.name) + '转换的数据为 ' + str(oct(subject.data)))     class DecimalViewer:     """updates the Decimal viewer"""       def update(self, subject):         print('DecimalViewer十进制查看器: 实验对象 % s 转换的数据为 % d' % (subject.name, subject.data))     """main function"""

　　

main.py 调用：

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

# 观察者模式  Observer Pattern obj1 = GeovinDuObserver.Data('Data 1') obj2 = GeovinDuObserver.Data('Data 2')   view1 = GeovinDuObserver.DecimalViewer() view2 = GeovinDuObserver.HexViewer() view3 = GeovinDuObserver.OctalViewer()   obj1.attach(view1) obj1.attach(view2) obj1.attach(view3)   obj2.attach(view1) obj2.attach(view2) obj2.attach(view3)   obj1.data = 10 obj2.data = 15   print("\n")

　　

输出：

?

1 2 3 4 5 6

DecimalViewer十进制查看器: 实验对象 Data 1 转换的数据为  10 HexViewer十六进制查看器: 实验对象 Data 1 转换的数据为： 0xa OctalViewer八进制查看器: 实验对象Data 1转换的数据为 0o12 DecimalViewer十进制查看器: 实验对象 Data 2 转换的数据为  15 HexViewer十六进制查看器: 实验对象 Data 2 转换的数据为： 0xf OctalViewer八进制查看器: 实验对象Data 2转换的数据为 0o17