What is the example of Observer?

Observer is a behavioral pattern. Decorator is a structural pattern . Using observer implements event handling (it binds some method calls of different classes with each other).

The Observer Pattern is the foundation of the Model View Controller (MVC) pattern, in which a view is updated automatically whenever the model’s state changes . … The subject interface defines a contract for attaching and detaching an observer to the subject, as well as notification of changes to any attached observers.

In general, the most relevant SOLID principle related to Observer is the Open/Close Principle : Once you have written the code of the observed object, you need not change the code when you want additional observers to know it, yet it is easy to add such observers – this is exactly what “closed for modifications, open …

What is the relationship between observer pattern and MVC? … First version is that, MVC is an architecture and Observer Pattern is an design pattern. They look similar because MVC uses the observer pattern. Second version is that, observer pattern and MVC is two different design patterns .

Observer is a behavioral design pattern that lets you define a subscription mechanism to notify multiple objects about any events that happen to the object they’re observing.