C Motivation

We do set 2 simple aims:

1. Simplify things
2. Reduce dependecies

The questions are: What we want to simplify? What dependencies we want to remove?

Say, you want a class to produce events and another class to consume them... Have a look at the classic observer pattern (a.k.a. Publish/subscribe or pub/sub):

Let's define those abstractions in a simple code:

1

public interface Subject {
    public void attach(Observer aListener);
}								
								

2

To be able to distribute evens among any class implementing a specific interface, you have to have an abstract observer interface

public interface Observer {
    public void update();
}
								

3

Now, let's implements something..
If you want a class be able to produce events, you have to maintain a collection of observers (event listeners). Furthermore, you have to maintain the event distribution process itself:

import java.util.Collection;


public class ConcreteSubject implements Subject{
    private Collection<Observer> observers;
    //.....
    public void attach(Observer observer) {
        observers.add(observer);
    }
    //.....
    public void notifyObservers(){
        for(Observer observer: observers){
            observer.update();
        }
    }
}
								

4

Off course, you need an observer implementation. Not a big deal!

public class ConcreteObserver implements Observer{

    public void update() {
        // DO something really useful
    }

}								
								

5

Finally, you need something to assemble the things together and make it run:

public class Assembler {
    public void runIt(){
        Subject subject=new ConcreteSubject();
        Observer observer=new ConcreteObserver();
        
        subject.attach(observer);      
    }
}

								

Now let's see what we have.. We do have the 5 classes coupled together.

1. ConcreteSubject + Observer + Subject
2. ConcreteObserver+ ConcreteObserver + Subject
3. Observer + Subject
4. Assemler + ConcreteSubject + ConcreteObserver

So, we have 5 classes with about 6 dependencies among them.

 

Macaroni framework provides little bit simplier model:

TODO

TODO

TODO