View source for OTExample Observer/ObservingOpen

'''Application of the Observer pattern'''

This team binds the [[OTExample Observer/ObserverPattern|ObserverPattern]]:
* The Subject role is played by [[OTExample Observer/Flower|Flower]]
* The Observer role is played by [[OTExample Observer/Bee|Bee]] and [[OTExample Observer/Hummingbird|Hummingbird]]

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

<source lang="otj" line="1">
package flower_example;

import protocol.ObserverPattern;
/**
 * @author Bruce Eckel (original Java example)
 * @author Miguel P. Monteiro (adaptation to OT/J)
 */
public team class ObservingOpen extends ObserverPattern {

    protected class Subject playedBy Flower
    {
        // This method  implicitly uses a private field of its base class: isOpen
        @Override
        @SuppressWarnings({ "inferredcallout", "decapsulation" })
        public void changeOp() {
            // manual implementation, see ObservingClose.Subject for an abbreviation.
            if(!isOpen)
                tsuper.changeOp();
        }
        changeOp <- before open;
    }

    public class BeeObserver extends Observer playedBy Bee {
        update -> haveBreakfast;
    }

    public class HummingbirdObserver extends Observer playedBy Hummingbird {
        update -> breakfastTime;
    }

    // This and the following signature applies OTJLD §2.3.2(e):
    public <AnyBase base Observer>
    void mapSubject2Observer(Flower as Subject subject, AnyBase as Observer observer) {
        subject.addObserver(observer);
    }

    public <AnyBase base Observer>
    void removeObserverFromSubject(Flower as Subject subject, AnyBase as Observer observer) {
        subject.removeObserver(observer);
    }

    public void removeAllObserversFromSubject(Flower as Subject subject) {
        subject.removeAllObservers();
    }
}
</source>

'''Explanation:'''
''soon''