python设计模式---行为型之观察者模式

比较常用咯~~

from django.test import TestCase
from abc import ABCMeta, abstractmethod

# 行为型设计模式---观察者模式
class Subject:
    def __init__(self):
        self._observers = []

    def register(self, observer):
        self._observers.append(observer)

    def notify_all(self, *args, **kwargs):
        for observer in self._observers:
            observer.notify(self, *args, **kwargs)

class ObserverA:
    def __init__(self, subject):
        subject.register(self)

    def notify(self, subject, *args):
        print(type(self).__name__, ':: Got ', args, ' From ', subject)

class ObserverB:
    def __init__(self, subject):
        subject.register(self)

    def notify(self, subject, *args):
        print(type(self).__name__, ':: Got ', args, ' From ', subject)

subject = Subject()
ob1 = ObserverA(subject)
ob2 = ObserverB(subject)
subject.notify_all('notification')

class NewsPublisher:
    def __init__(self):
        self._subscribers = []
        self._latest_news = None

    def attach(self, subscriber):
        self._subscribers.append(subscriber)

    def detach(self):
        return self._subscribers.pop()

    def subscribers(self):
        return [type(x).__name__ for x in self._subscribers]

    def notify_subscribers(self):
        for sub in self._subscribers:
            sub.update()

    def add_news(self, news):
        self._latest_news = news

    def get_news(self):
        return 'Got News: ', self._latest_news

class Subscriber(metaclass=ABCMeta):

    @abstractmethod
    def update(self):
        pass

class SMSSubscriber:
    def __init__(self, publisher):
        self.publisher = publisher
        self.publisher.attach(self)

    def update(self):
        print(type(self).__name__, self.publisher.get_news())

class EmailSubscriber:
    def __init__(self, publisher):
        self.publisher = publisher
        self.publisher.attach(self)

    def update(self):
        print(type(self).__name__, self.publisher.get_news())

class AnyOtherSubscriber:
    def __init__(self, publisher):
        self.publisher = publisher
        self.publisher.attach(self)

    def update(self):
        print(type(self).__name__, self.publisher.get_news())

news_publisher = NewsPublisher()
for Subscribers in [SMSSubscriber, EmailSubscriber, AnyOtherSubscriber]:
    Subscribers(news_publisher)

print('Subscribers: ', news_publisher.subscribers())
news_publisher.add_news('Hello, world!')
news_publisher.notify_subscribers()

print('Detached: ', type(news_publisher.detach()).__name__)
print('Subscribers: ', news_publisher.subscribers())

news_publisher.add_news('My second news!')
news_publisher.notify_subscribers()

　　

ObserverA :: Got  ('notification',)  From  <__main__.Subject object at 0x0000000002A2BF28>
ObserverB :: Got  ('notification',)  From  <__main__.Subject object at 0x0000000002A2BF28>
Subscribers:  ['SMSSubscriber', 'EmailSubscriber', 'AnyOtherSubscriber']
SMSSubscriber ('Got News: ', 'Hello, world!')
EmailSubscriber ('Got News: ', 'Hello, world!')
AnyOtherSubscriber ('Got News: ', 'Hello, world!')
Detached:  AnyOtherSubscriber
Subscribers:  ['SMSSubscriber', 'EmailSubscriber']
SMSSubscriber ('Got News: ', 'My second news!')
EmailSubscriber ('Got News: ', 'My second news!')