We wrap up the season with the observer pattern and a review of what we have learned.  This pattern is one that you probably have already encountered.  Instead of an observer, you probably have heard it called a listener.

The Observer Pattern Defined

As always, we will start with the “Gang of Four” intent to set the stage for our discussion.

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