Accessing Multiple Observers in an Observable class

Question

Hi! I have 2 Observers added via:
this.addObserver() on my 1 Observable class.
The 1st Observer works fine when i call:
setChanged();
notifyObservers("SomeArgument");However, when i pass a different argument to the 2nd Observer that i added, it still uses the first Observer...
So, I am wondering what i am doing wrong - how can i access the 2nd Observer in this class?
I hope that I am being clear enough on this!
Regards

Answer 1

wizzkidd wrote:
I think what i am trying to get across is lost in translation!
ok, here goes
The Observable class has calls such as:
setChanged();
notifyObservers("AnEvent");     
// Something else happens...
setChanged();
notifyObservers("AnotherEvent");     
Normally this is done inside one of the methods of the Observable. I have to assume you are doing this since notifyObservers() is protected.
Each of these notifications will go to ALL registered Observers. You cannot pick and choose since this would break the decoupling in the Observables between the Observables and the Observers.
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Now, i want to assign Observers to this Observable class via:
addObserver(objectObserver1);
addObserver(objectObserver2);
Yep, standard. So ALL notifications will go to both objectObserver1 and objectObserver2 .
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So, how can I indicate that the observer i want to use is objectObserver2?This does not make sense. objectObserver2 is the observer.
>
Now after writing this - i see what you are saying when you state:
The Observable knows nothing about the Observers but the Observers know about the Observable.but by supplying an argument e.g. notifyObservers("AnotherEvent"); i am breaking that rule. Correct?
Is this the intended use of the argument in notifyObservers() or is there another way of determining which Observer to use that i am missing?There is not concept of "which Observer to use" . Any notification of 'events' will go to ALL registered observers by invoking thevoid update(Observable o,
            Object arg) method on the Observer.
If some Observers don't wish to process a particular event then they don't have to. In the update() method of my Observers I have a short set of 'if' statements so as to select select which notification events they need to process.
Edited by: sabre150 on Oct 22, 2008 10:44 AM