Design Pattern - Observer

# Observer podle diagramu http://voho.cz/wiki/observer/

from abc import ABCMeta, abstractmethod

# Abstraktni Observer
class Observer():
    __metaclass__=ABCMeta

    @abstractmethod
    def update():
        pass

# Konkrenti observery
class ConcreteObserver1(Observer):
    def __init__(self):
        print("Byl zalozen objekt ConcreteObserver1.")

    def update(self):
        print("ConcreteObserver1: Detekovana udalost!")

class ConcreteObserver2(Observer):
    def __init__(self):
        print("Byl zalozen objekt ConcreteObserver2.")

    def update(self):
        print("ConcreteObserver2: Detekovana udalost!")

# Abstraktni Observable
class Observable():
    __metaclass__=ABCMeta

    observers = []

    def attach(self, obs):
        Observable.observers.append(obs)

    def detach(self, obs):
        pass

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

class ConcreteObservable(Observable):
    '''
    Pozorovany objekt - vyuziva metody abstraktni tridy Observable
    '''
    def __init__(self):
        print("Byl zalozen objekt ConcreteObservable.")

class Client():
    '''
    Klientsky objekt - jakykoliv obj, ktery chce nejaky jiny pozorovat
    '''

    def __init__(self, obs):
        self.concreteObservable = obs

        print("Byl zalozen objekt Client.")

    def action(self):
        self.concreteObservable.notify()

if __name__ == '__main__':
    concreteObservable = ConcreteObservable()
    concreteObserver1 = ConcreteObserver1()
    concreteObserver2 = ConcreteObserver2()

    client = Client(concreteObservable)

    # Test upozorneni - pridam oba observery
    concreteObservable.attach(concreteObserver1)
    concreteObservable.attach(concreteObserver2)

    client.action()