Question

1. What is an Observer Design Pattern?

2. List when to use this design patter?

3. List why we don't want to use this design pattern.

Answer 1

The observer pattern is a software design pattern in which an object, called the subject, maintains a list of it's dependents, called observers, and notified them automatically of any state changes, usually by calling one of their methods.

It is mainly used to implement distributed event handling systems, in "event driven" software. Most modern languages such as c# have built in "event" constructs which implement the observer pattern components.

The observer pattern is also a key part in the familiar model-view-controller architectural pattern. The observer pattern is implemented in numerous programming libraries and systems, including almost all GUI toolkits.

Design patterns are supposed to provide a structure in which problems can be solved. When solving a real problem, you have to consider many tiny variations of a solution to that problem to see whether any fits a design pattern. In particular , you will probably need to generalise your problem, or it's solution in order to make a design pattern fit.

Knowing the design patterns is certainly an important step.