Observer Design Pattern

Imagine you are in a movie theater and want to be notified when the next show starts. You can sign up for a notification service by giving them your phone number. Whenever the next show starts, the theater sends a text message to all the subscribers. That's the idea behind the Observer Design Pattern.

Here's how the Observer Design Pattern works:
You have a subject or observable object, which is the movie theater in this example.
You have one or more observers, which are the people who have signed up for notifications.
The subject maintains a list of its observers and provides a method for adding or removing observers.

Whenever the subject changes its state, it notifies all its observers, who can then respond to the change. So in the movie theater example, the movie theater is the subject, and the people who have signed up for notifications are the observers. The movie theater maintains a list of the observers and sends a text message to all of them whenever the next show starts.

This pattern provides several benefits:
It allows objects to be loosely coupled, which makes it easier to modify and maintain the code.
It enables objects to respond to changes in other objects without having to know the details of those objects.
It can improve performance by reducing the amount of data that needs to be passed between objects.

In summary, the Observer Design Pattern is a useful tool for allowing objects to observe and respond to changes in other objects. It helps ensure loose coupling and maintainability in your code, and can be a valuable tool for improving performance.