Every Software Engineer certainly must have to deal with change. Change is a constant in Software Design : Adding feature, Changing of requirement, or Bug fixing.
What is design pattern ? In simplest way I can say, it is general solutions for common problem in Software Development. The purpose of design pattern is to help structure your code so it will be flexible and resilient when its changed.
There are 23 Common Design Pattern that being used by programmer around the world, in this chapter I am going to describe about Observer Pattern.