app/DB/observer.py

   1 import abc
   2
   3 class WeatherSubject(metaclass=abc.ABCMeta):
   4     @abc.abstractmethod
   5     def add_observer(self, weather_observer):
   6         pass
   7
   8     @abc.abstractmethod
   9     def remove_observer(self, weather_observer):
  10         pass
  11
  12     @abc.abstractmethod
  13     def do_notify(self):
  14         pass
  15
  16
  17 class WeatherObserver(metaclass=abc.ABCMeta):
  18     @abc.abstractmethod
  19     def do_update(self, temperature):
  20         pass
  21
  22
  23 class WeatherStation(WeatherSubject):
  24     def __init__(self, temperature):
  25         self.observers = []
  26         self.temperature = temperature
  27
  28     def add_observer(self, weather):
  29         self.observers.append(weather)
  30
  31     def remove_observer(self, weather):
  32         self.observers.remove(weather)
  33
  34     def do_notify(self):
  35         for observer in self.observers:
  36             observer.do_update(self.temperature)
  37
  38     def set_temperature(self, temperature):
  39         print("Weather station setting temperature to %s" % temperature)
  40         self.temperature = temperature
  41         self.do_notify()
  42
  43
  44 class WeatherCustomer1(WeatherObserver):
  45     def do_update(self, temperature):
  46         print("Weather customer 1 just found out the temperature is: %s" % temperature)
  47
  48
  49 class WeatherCustomer2(WeatherObserver):
  50     def do_update(self, temperature):
  51         print("Weather customer 2 just found out the temperature is: %s" % temperature)
  52
  53
  54 if __name__ == '__main__':
  55     station = WeatherStation(33)
  56
  57     wc1 = WeatherCustomer1()
  58     wc2 = WeatherCustomer2()
  59     station.add_observer(wc1)
  60     station.add_observer(wc2)
  61
  62     station.set_temperature(34)
  63     station.remove_observer(wc1)
  64     station.set_temperature(35)