observer

Observer

Observer Pattern allows observers to be notified on changes in an observable object.

Code

CourseWebsite (an Obserable object) allows Students to register as an Observer. When CourseWebsite has a new state update, e.g. PutAnnoucement() is called, it notifies all registered Observer by calling its Update().

Example

CourseWebsite course_website;

Student olivia("Olivia");
Student liam("Liam");
course_website.AddObserver(olivia);
course_website.AddObserver(liam);

course_website.PutAnnoucement("New assignment is released!");

Output:

This is Olivia. I just received an update from the course website saying: New
assignment is released!
This is Liam. I just received an update from the course website saying: New
assignment is released!

Reference

• https://stackoverflow.com/questions/10069299/observer-design-pattern
• https://stackoverflow.com/questions/13744450/when-should-we-use-observer-and-observable