The Observer Design Pattern is a behavioral design pattern that defines a one-to-many dependency between objects. When one object (the subject) changes its state, all its dependents (observers) are notified and updated automatically. This pattern is widely used in software engineering to establish communication between objects in a loosely coupled manner.
This Design Pattern is widely used for implementing distributed event-handling systems where an object needs to notify other objects about its state changes without knowing who these objects are.
In the Observer Design Pattern, an object (called a Subject) maintains a list of its dependents (called Observers). It notifies them automatically whenever any state changes by calling one of their methods. The Other names of this pattern are Producer/Consumer and Publish/Subscribe.
Components of Bridge Design Pattern
- Subject: This is the object that is being observed. It maintains a list of observers and provides methods to attach, detach, and notify observers of state changes.
- Observer: This is the interface that defines the method(s) that the subject will use to notify observers of state changes.
- ConcreteSubject: This is the concrete implementation of the subject. It maintains the state of interest and notifies observers when changes occur.
- ConcreteObserver: This is the concrete implementation of the observer. It registers itself with the subject and implements the update method to react to changes in the subject's state.
