What do you mean by observer pattern?
If several objects are tied together in one-to-many relationships, the observer pattern is used. Every time one object is modified, then all of its dependent objects are automatically notified and updated. It falls under the behavioural pattern category. It describes the coupling between the objects and the observer and provides support for broadcast-type communication. The object that observes the state of another object is known as the observer, and the object that is being observed is known as the subject.
