OTExample Observer/ObservingOpen

Application of the Observer pattern

This team binds the ObserverPattern:

• 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 ObservingOpen extends ObserverPattern {

10.     protected class Subject playedBy Flower

11.     {

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

13.         @Override

14.         @SuppressWarnings({ "inferredcallout", "decapsulation" })

15.         public void changeOp() {

16.             // manual implementation, see ObservingClose.Subject for an abbreviation.

17.             if(!isOpen)

18.                 tsuper.changeOp();

19.         }

20.         changeOp <- before open;

21.     }

23.     public class BeeObserver extends Observer playedBy Bee {

24.         update -> haveBreakfast;

25.     }

27.     public class HummingbirdObserver extends Observer playedBy Hummingbird {

28.         update -> breakfastTime;

29.     }

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

32.     public <AnyBase base Observer>

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

34.         subject.addObserver(observer);

35.     }

37.     public <AnyBase base Observer>

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

39.         subject.removeObserver(observer);

40.     }

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

43.         subject.removeAllObservers();

44.     }

45. }

Explanation: soon