MVC: info on update method

Question

Hi,
I'm using MVC pattern.
I've understood it, and I be able to use it, but I've some doubts.
Practically, in the view I have the update method;
Now, my view interact with many models, which advice it by executing his update method.
But in this update method, I've various pieces of code;
one for the update of the first model;
one for the update of the second model;
etc.....
I don't like this, because I want that,
when a model is updated, it advice view by executing only the corresponding piece of code.
Is there any other solution?
Excuse me if it's not clear.
Thank you in advance
MargNat

Answer 1

I take it from your message that you're implementing a Swing-based MVC GUI (things would be hardly different for a Web MVC application).
In this Swing GUI, the View is an Observer of the Model, hence your update() method, correct?
Indeed you don't have to apply this blindly : you may very well have each model have its own Observer interface; indeed in the Java world, an Observer is usually implemented as a "Listener" idiom, which provides more strongly typed notification methods.
So you can have your ModelA notify a (set of) ModelAListener object where ModelAListener is an interface providing a modelAUpdated(ModelA model), same for ModelB and ModelC.
Then your view ony has to implement ModelAListener, ModelBListener, ModelCListener, and provide model-specific code in each model-specific method modelAUpdated(ModelA), modelBupdated(ModelB), modelCUpdated(ModelC).
SO when the ModelC instance is updated, it invopkes it's listener's modelCUpdated(ModelC) method, which only takes care of ModelC's changes.
All 3 methods could even have the same name modelUpdated(...) or update(...), with a different type of parameter each, the overloading specifying which Model has changed (but IMHO this would go against clarity of the code).