How do I implement the Observer Pattern in my application?

How do I implement the Observer Pattern in my application?

The Observer Pattern is a behavioral design pattern that allows an object, known as the subject, to maintain a list of its dependents, called observers, and notify them of any state changes. Would you like a code example?

Yes, please provide a code example in Python.

Sure! Here's a simple implementation in Python:

class Subject:
    def __init__(self):
        self._observers = []

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

    def detach(self, observer):
        self._observers.remove(observer)

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

class Observer:
    def update(self):
        print("Observer has been notified!")

# Usage
subject = Subject()
observer1 = Observer()
subject.attach(observer1)
subject.notify()  # Output: Observer has been notified!

This code defines a Subject that can attach and notify observers.

What are some real-world applications of the Observer Pattern?

The Observer Pattern is commonly used in event handling systems, like GUI frameworks, where UI components need to respond to user actions. It's also used in implementing publish-subscribe systems, such as messaging services.