Source Code for Module pypat.behavioral.observer

 1  from abc import ABCMeta, abstractmethod 
 2   
 3   
 4 -class Observer(object, metaclass=ABCMeta): 
 5      """ 
 6      Abstract Observer class as part of the Observer design pattern. 
 7   
 8      - External Usage documentation: U{https://github.com/tylerlaberge/PyPatterns/wiki/Behavioral-Pattern-Usage} 
 9      - External Observer Pattern documentation: U{https://en.wikipedia.org/wiki/Observer_pattern} 
10      """ 
11      @abstractmethod 
12 -    def update(self, **state): 
13          """ 
14          Abstract method that is called when an Observable's state changes. 
15          """ 
16          pass 
17   
18   
19 -class Observable(object): 
20      """ 
21      Base Observable class as part of the Observer design pattern. 
22   
23      - External Usage documentation: U{https://github.com/tylerlaberge/PyPatterns/wiki/Behavioral-Pattern-Usage} 
24      - External Observer Pattern documentation: U{https://en.wikipedia.org/wiki/Observer_pattern} 
25      """ 
26 -    def __init__(self): 
27          """ 
28          Initialize a new Observable instance. 
29          """ 
30          self._observers = set() 
31   
32 -    def attach(self, observer): 
33          """ 
34          Attach an observer to this Observable. 
35   
36          @param observer: The Observer to attach. 
37          @type observer: Observer 
38          """ 
39          self._observers.add(observer) 
40   
41 -    def detach(self, observer): 
42          """ 
43          Detach an observer from this Observable. 
44   
45          @param observer: The Observer to detach. 
46          @type observer: Observer 
47          """ 
48          try: 
49              self._observers.remove(observer) 
50          except KeyError: 
51              pass 
52   
53 -    def notify(self): 
54          """ 
55          Notify all attached Observers of the state of this Observable. 
56          """ 
57          for observer in self._observers: 
58              state = {k: v for k, v in self.__dict__.items() if not k.startswith('__') and not k.startswith('_')} 
59              observer.update(**state) 
60