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observerpatter.py
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observerpatter.py
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from __future__ import annotations
from abc import ABC, abstractmethod
class StockObservable(ABC):
@abstractmethod
def add(self, observer):
pass
@abstractmethod
def remove(self, observer):
pass
@abstractmethod
def notify_subscriber(self):
pass
@abstractmethod
def set_stock_count(self, newStockAdded):
pass
@abstractmethod
def get_stock_count(self):
pass
class IphoneObservable(StockObservable):
stock_count = 0
observers = []
def add(self, observer):
self.observers.append(observer)
def remove(self, observer):
self.observers.remove(observer)
def notify_subscriber(self):
for observer in self.observers:
observer.update()
def set_stock_count(self, new_stock_added):
if self.stock_count == 0:
self.notify_subscriber()
self.stock_count += new_stock_added
def get_stock_count(self):
return self.stock_count
class NotificationAlertObserver(ABC):
@abstractmethod
def update(self):
pass
class EmailAlertObserver(NotificationAlertObserver):
_emailId = ''
_observable = None
def __init__(self, email_id, observable):
self._observable = observable
self.email_id = email_id
def update(self):
self.send_message(self.email_id, 'product is back in stock')
def send_message(self, email_id, msg):
print('email sent to:', email_id)
class MobileAlertObserver(NotificationAlertObserver):
mobile_no = ''
observable = None
def __init__(self, mobile_no, observable):
self.observable = observable
self.mobile_no = mobile_no
def update(self):
self.send_message(self.mobile_no, 'product is back in stock')
def send_message(self, mobile_no, msg):
print('msg sent to mobile no.:', mobile_no)
if __name__ == '__main__':
iphone_stock_observable = IphoneObservable()
observer1 = EmailAlertObserver('abc@gmail.com', iphone_stock_observable)
observer2 = EmailAlertObserver('xyz@gmail.com', iphone_stock_observable)
observer3 = MobileAlertObserver('1122334455', iphone_stock_observable)
iphone_stock_observable.add(observer1)
iphone_stock_observable.add(observer2)
iphone_stock_observable.add(observer3)
iphone_stock_observable.set_stock_count(10)
iphone_stock_observable.set_stock_count(-10)
iphone_stock_observable.remove(observer2)
iphone_stock_observable.set_stock_count(40)
print('Current stock count:', iphone_stock_observable.get_stock_count())