Design-Patterns/observer.py at master · mohabmes/Design-Patterns · GitHub

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
from abc import ABC, abstractmethod

class Observer(ABC):

    @abstractmethod
    def update()-> None:
    	pass


class Subject(ABC):

    def __init__(self):
    	self.observers = []


    def registerObserver(self, observer : Observer) -> None:
    	self.observers.append(observer)
    	print(id(observer), ": Subscribed")


    def unregisterObserver(self, observer : Observer) -> None:
    	self.observers.remove(observer)
    	print(id(observer), ": Unsubscribed")


    def notify(self):
    	for observer in self.observers:
    		observer.update()


class Subscriber(Observer):

    def update(self) -> None:
    	print(id(self), ": New post notification")


class Blog(Subject):

    def getSubscriberCount(self) -> int:
    	return len(self.observers)

    def newPost(self) -> None:
    	print("create new post .. ")
    	self.notify()


sub1 = Subscriber()
sub2 = Subscriber()

blog = Blog()
blog.registerObserver(sub1)
blog.registerObserver(sub2)

print(blog.getSubscriberCount())

blog.newPost()
blog.unregisterObserver(sub2)
print(blog.getSubscriberCount())