Key Concepts of Observer Method Design Pattern

The key concepts of the Observer Pattern are:

• Subject: The subject is the object that maintains a list of its dependents, also known as observers.It provides an interface for attaching, detaching, and notifying observers.
• Observer: The observer is the interface that defines the update method, which is called by the subject to notify the observer of a change in the subject’s state.Observers register themselves with the subject to receive updates.
• ConcreteSubject: The concrete subject is a concrete implementation of the subject interface. It maintains the state of interest and notifies observers when a change occurs.
• ConcreteObserver: The concrete observer is a concrete implementation of the observer interface. It registers itself with a subject to receive updates and implements the update method to respond to changes in the subject’s state.
• Observer List:The subject maintains a list (or collection) of observers, allowing multiple observers to be notified of changes.
• Loose Coupling: The Observer Pattern promotes loose coupling between the subject and its observers. The subject doesn’t need to know the details of its observers, and observers can be added or removed without affecting the subject.

Observer Design Pattern is a behavioral design pattern where an object, known as the subject, maintains a list of its dependents, called observers, that are notified of any changes in the subject’s state. This pattern is often used to implement distributed event handling systems.