© Vaskaran Sarcar 2020
V. SarcarDesign Patterns in C#https://doi.org/10.1007/978-1-4842-6062-3_14

14. Observer Pattern

Vaskaran Sarcar1 
Garia, Kolkata, West Bengal, India

This chapter covers the Observer pattern.

GoF Definition

Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically.


In this pattern, there are many observers (objects) that are observing a particular subject (also an object). Observers want to be notified when there is a change made inside the subject. So, they register for that subject. When they lose interest in the subject, they simply unregister from the subject. Sometimes this model is called a Publisher-Subscriber (Pub-Sub) model ...

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