Re: (Class>) casting troubles

[Sebastiaan van Erk]

Johan Compagner wrote:

yes i also thought about some time ago.

But this is not really better... Now without you doing a cast in the code
(so that you know what you are doing)
you suddenly have a class cast exception at some point later on


class MyComp extends Component {
       public MyComp() {
           IModel<Integer> model = getModel();
           Integer myInt = model.getObject(); // KABOOM

       }

because this thing gives you really a false kind of protection.

This is really an abuse of generics if you ask me..

When I think about it, I have to agree. You can do ugly stuff like:

IModel<Integer> x = getModel();
IModel<Double> y = getModel();

and it will compile just fine... :-(

I'd rather have no generics than a dirty hack like this.

Regards,
Sebastiaan

johan

On Wed, May 21, 2008 at 3:01 PM, Joni Freeman <[EMAIL PROTECTED]> wrote:

On Wed, 2008-05-21 at 14:44 +0200, Sebastiaan van Erk wrote:

Martijn Dashorst wrote:

Generified component touches *ALL* code in Wicket, wether you care or
not. IModel<T> itself is rather contained.

Yes, but in my opinion rather useless as well. Plus you get heaps of
@SuppressWarnings all over the place. Then just get rid of generics
completely...

In which case would you need @SuppressWarnings? Consider for instance:

   interface IModel<T> {
   }

   class Component {
       private IModel<?> model;

       public <T> IModel<T> getModel() {
           return (IModel<T>) model;
       }
   }

   class MyComp extends Component {
       public MyComp() {
           IModel<Integer> model = getModel();
       }
   }

This compiles and the only warning is within wicket code. There's an
unsafe cast to IModel<T>. Of course this would mean that getModel and
getModelObject could throw classcastexception. It's a tradeoff: simple
and more conservative usage of generics vs. fully type safe but complex
and verbose usage of generics.

Joni







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