This.FavoritePlayerPoints = Ĭonsole.WriteLine( + ' has ' + this. Public BasketballFan(BasketballPlayer player) This.ObserverState = MySubject.SomeState Ĭonsole.WriteLine('My state has been updated: ' + this.ObserverState) īasketballPlayer damianLillard = new BasketballPlayer('Damian Lillard') īasketballFan basketballFan1 = new BasketballFan(damianLillard) īasketballFan basketballFan2 = new BasketballFan(damianLillard) Public ConcreteObserver(ConcreteSubject subject) Stores state that should stay consistent with the ConcreteSubject.ĬoncreteSubject subject = new ConcreteSubject() ĬoncreteObserver observer = new ConcreteObserver(subject).Stores reference to the ConcreteSubject.Notifies the observers when the state changes.Defines the Attach, Detach, and Notify methods.Now, in object oriented software design, two (of the many) problems that arise. To achieve the observer pattern, there are four types of classes we need to implement: For example, in their original (Alexandrian) setting each pattern was an. Each observer keeps a reference to the subject, stores the state that should be consistent with the subject’s, and implements the observer updating the interface to keep the state consistent with that of the subject. The subject holds whatever state is of interest and notifies the observers when the state changes. In this pattern, there is one subject and many observers. The observer pattern allows us to create a one-to-many relationship between objects so that when one object changes, the many objects observing it will be notified and update accordingly. Observer: a thing that watches or notices something. I’ll first give a definition of the pattern, then show its implementation in C#, and finish with a code example.

This time we’ll be taking a look at the observer pattern that is a behavioral pattern. My first two posts covered creational design patterns.

Wassup! This is the third post that I’m writing while learning design patterns.

Observer design pattern example