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Source Code for Module smartcard.Observer

 1  """ 
 2  from Thinking in Python, Bruce Eckel 
 3  http://mindview.net/Books/TIPython 
 4   
 5  Class support for "observer" pattern. 
 6   
 7  The observer class is the base class 
 8  for all smartcard package observers. 
 9   
10  Known subclasses: 
11          smartcard.ReaderObserver 
12   
13  """ 
14   
15  from smartcard.Synchronization import * 
16   
17   
18 -class Observer: 
19   
20 -    def update(observable, arg): 
21          '''Called when the observed object is 
22          modified. You call an Observable object's 
23          notifyObservers method to notify all the 
24          object's observers of the change.''' 
25          pass 
26   
27   
28 -class Observable(Synchronization): 
29   
30 -    def __init__(self): 
31          self.obs = [] 
32          self.changed = 0 
33          Synchronization.__init__(self) 
34   
35 -    def addObserver(self, observer): 
36          if observer not in self.obs: 
37              self.obs.append(observer) 
38   
39 -    def deleteObserver(self, observer): 
40          self.obs.remove(observer) 
41   
42 -    def notifyObservers(self, arg=None): 
43          '''If 'changed' indicates that this object 
44          has changed, notify all its observers, then 
45          call clearChanged(). Each observer has its 
46          update() called with two arguments: this 
47          observable object and the generic 'arg'.''' 
48   
49          self.mutex.acquire() 
50          try: 
51              if not self.changed: 
52                      return 
53              # Make a local copy in case of synchronous 
54              # additions of observers: 
55              localArray = self.obs[:] 
56              self.clearChanged() 
57          finally: 
58              self.mutex.release() 
59          # Update observers 
60          for observer in localArray: 
61              observer.update(self, arg) 
62   
63 -    def deleteObservers(self): 
64              self.obs = [] 
65   
66 -    def setChanged(self): 
67              self.changed = 1 
68   
69 -    def clearChanged(self): 
70              self.changed = 0 
71   
72 -    def hasChanged(self): 
73              return self.changed 
74   
75 -    def countObservers(self): 
76              return len(self.obs) 
77   
78  synchronize(Observable, 
79      "addObserver deleteObserver deleteObservers " + 
80      "setChanged clearChanged hasChanged " + 
81      "countObservers") 
82  #:~ 
83   

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