OTExample Observer/ObservingClose

Application of the Observer pattern

This team is a slight variation of ObservingOpen, also binding the ObserverPattern like this:

• The Subject role is played by Flower
• The Observer role is played by Bee and Hummingbird

A few comments are given inline, for more explanation see below.

1. package flower_example;

3. import protocol.ObserverPattern;

4. /**

5.  * @author Bruce Eckel (original Java example)

6.  * @author Miguel P. Monteiro (adaptation to OT/J)

7.  */

8. public team class ObservingClose extends ObserverPattern {

10.     protected class Subject playedBy Flower

11.     {

12.         // This method binding uses a private field of its base class: isOpen

13.         @SuppressWarnings("decapsulation")

14.         changeOp <- before close

15.             base when (base.isOpen);

16.     }

18.     public class BeeObserver extends Observer playedBy Bee {

19.         update -> goToBed;

20.     }

22.     public class HummingbirdObserver extends Observer playedBy Hummingbird {

23.         update -> bedTime;

24.     }

26.     // This and the following signature applies OTJLD §2.3.2(e):

27.     public <AnyBase base Observer>

28.     void mapSubject2Observer(Flower as Subject subject, AnyBase as Observer observer) {

29.         subject.addObserver(observer);

30.     }

32.     public <AnyBase base Observer>

33.     void removeObserverFromSubject(Flower as Subject subject, AnyBase as Observer observer) {

34.         subject.removeObserver(observer);

35.     }

37.     public void removeAllObserversFromSubject(Flower as Subject subject) {

38.         subject.removeAllObservers();

39.     }

40. }

Differences to ObservingOpen

soon