Re: wicket generics

[Sebastiaan van Erk]

I'm +1 for trying to decouple model from component, and if it takes longer then so be it.

Regards,
Sebastiaan

Igor Vaynberg wrote:

I'm pretty convinced that the problem is the 1-1 model-component coupling and that generics only pointed out this problem.

so i tried to remove the generic type from component in
sandbox/ivaynberg/wicket-generics branch and ran into what i think is
a deal breaker for this design

class component {
  public void setmodel(imodel<?> model) {...}
  public imodel<?> getmodel();
}

that is all good until you want to have a generified subclass eg a listitem:

class listitem<t> extends component {
  public imodel<t> getmodel() { return (imodel<t>)super.getmodel(); }
<== works like a charm
  public void setmodel(imodel<t> model) {..} <== woops, compilation error

Name clash: The method setModel(IModel<T>) of type ListItem<T> has the
same erasure as
 setModel(IModel<?>) of type MarkupContainer but does not override it

unfortunately the error makes sense and there is no way around it.
same goes for setmodelobject(). i think this makes this design variant
pretty useless. as long as we have the model coupled to component i
dont see a clean way of doing this :(

class listitem<t> extends component {
  public imodel<t> getmodel(..);
  public void setmodel(imodel<?> model);
}

looks half baked and broken by design

i would almost reconsider 1.4 and its scope and opt to include a model
decoupling (however and if that is possible) refactor in it. otherwise
i fear we will break the whole generics model again in 1.5 and users
will have to relearn how to use them with wicket.

so as far as i can see, and this is only my opinion, our options are:

continue 1.4 as it is now with fully typed components
remove component type but make the api ugly ( i will let matej explain )
attempt to fix 1.4 by decoupling model from component - 1.4 takes a
lot longer and is not a simple "drop-in/upgrade/whatever"

thoughts and ideas?

-igor

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