Re: static or not?

iamfractal@xxxxxxxxxxx wrote:
Hi, Ed!

....
> Thus, for example, controller.Driver will register its Controller
> interface in the Registry by calling:
> Registry.getInstance().register(this).

package controller;
package-private class Driver extends controller.Controller{
void register() {
Registry.getInstance().register(this);
}
}
is the register method correct as far as it goes?


"If I use a singleton, then I can strip away an interface from this
singleton, and have it register that interface in the Registry.

If I use static methods, I cannot do this: static methods are not
allowed to hide the instance methods of the interface.

This is the major reason I use a singleton, instead of a class of
static methods. " -Ed

this is where you're stripping away an interface?

> Next, a user will make some input; we needn't specify how, here, but
> suffice it to say that when that input is made, an object will need to
> get that input into the system. It will do this by doing something
> like:
> Controller controller = Registry.getRegistry().getController();
> controller.process(input);

if this is done from class foo, what's foo's package? of MVC
I think view, but view presents data to the user, so I'm not sure.

> The Driver object will have its process() method called, and will kick
> the database into life, by something like:
> Registry registry = Registry.getInstance();
> Model model = registry.getModel();
> model.doThis();
> model.doThat();
> Result result = model.getResult();
>
> (OK, here's an interface I'd forgotten; any guesses where we'd declare
> it?)

heh, ir1 of course.

> The Driver object would then output the result to the use by:
> int viewID = registry.getCurrentViewID();
> View view = registry.getView(viewID);
> view.show(result);

where did result come from, please?
view.show() might trigger a SQL query and would show the outcome of
that query?

you said "...portray Driver as a Controller," so it's:

package controller;
package-private class Driver implements SomeInterface {...


> Thus we have a system in which there are only two types of
> inter-package, concrete class dependencies:
>
> 1) From Start to XStart - and these XStart classes only contain enough
> logic to kick start the business logic, in other words, these
> dependencies do not change as business logic changes.

if everything in the start package is business logic, might that
logic consist of static methods, like Math.sin(x), or is that a bit
extreme?

> 2) Dependencies on the Registry concrete class - but this class simply
> stores and erturns interfaces, and has no dependencies on the
> methods of those interfaces, and thus is immune to changes of the
> interface methods (although of course will change as whole
> interfaces change, and new ones are added).



> And *all* other inter-package dependencies are on interfaces
> only. Thus, you can switch in any database you like, as long as it
> conforms to the Model interface (this will, in reality, probably be
> JDBC, or a wrapper thereof). The same goes for the Views and even the
> Controller itself.
>
> Hence, "Program to an interface repository, not an implementation
> repository."
>
> Note that model package, view package, and controller packages do not
> depend on one another (you can Google for the heated discussions on
> which of these packages should depend on one another, and which must
> not), and that the system is guaranteed to be free from inter-package
> circular dependencies.

err, next time ;)

> Of course a full system will have hundreds of packages, and there will
> be hierarchical start/implementation repository/irX packages, but the
> design is - and particularly the benefits listed above are -
> wonderfully extensible.
>
> .ed
>
> www.EdmundKirwan.com - Home of The Fractal Class Composition.



this helps to justify MVC for me, thanks.



-Thufir

.

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