Igor Vaynberg wrote:
your link works on the object and not on the model, instead

add(new link("delete", item.getmodel()) { onclick() {
delete(getmodelobject()); }});


Thank you for your quick reply.

Well the code is roughly the same(?) as in Listing 5.12 of WiA and there
a custom Model is used to illustrate the solution. However, I thought my
test would show me the problem first... Using your code above, the
effect is as expected, i.e. the "wrong" (new) item is returned to be
deleted.

Now, the question is, what is wrong with my first implementation?
It would seem that the problem that is solved using a custom ItemModel
does not even occur. Or does that code prevent wicket from effectively
detaching model objects and should thus be avoided? What would be the
best practice here?


J.

-igor

On Thu, Oct 2, 2008 at 9:04 AM, Jürgen Lind <[EMAIL PROTECTED]> wrote:
Hi there,

I have been struggling for some time now to understand how
LoadableDetachableModel and a ListView work together. The starting point
was Chapter 5.5.2 of "Wicket in Action" where it is recommended to provide
your own ItemModel if the underlying list changes frequently. To try out
how Wicket behaves without such a custom ItemModel, I wrote the following
Test:

<body>
 <em wicket:id="listview">
   <span wicket:id="label"></span><a wicket:id="delete">delete</a>
 </em>
</body>


LoadableDetachableModel model = new LoadableDetachableModel() {

 @Override
 protected Object load() {
   System.out.println("load");
   return Arrays.asList(new TestItem[] {
       new TestItem("a" + Math.random()),
       new TestItem("b" + Math.random()),
       new TestItem("c" + Math.random()) });
 }

 protected void onDetach() {
   System.out.println("detach");
 }

};

ListView listview = new ListView("listview", model) {
 protected void populateItem(ListItem item) {
   final TestItem itemModel = (TestItem) item.getModelObject();
   item.add(new Label("label", itemModel.toString()));
   item.add(new Link("delete") {

     @Override
     public void onClick() {
       System.out.println("Delete " + itemModel);
     }
   });
 }
};

add(listview);


Now, I would expect that when I hit the "delete" link, Wicket would call the
"load" Method of the LoadableDetachableModel before printing "Delete..." as
the
default implementation will use the index and the list to determine the item
to
delete. To my surprise, however, the "Delete..." message is printed with the
correct item and the "load" Method is called afterwards. In my
understanding,
this contradicts the idea of the LoadableDetachableModel since Wicket seems
to
have a copy of the original list somewhere so that it can determine the list
item on which the action was invoked before loading the underlying list.

Can someone spot my mistake?

Thanks,

J.

--
Dr. Jürgen Lind
iteratec GmbH                Fon: +49 (0)89 614551-44
Inselkammerstrasse 4         Fax: +49 (0)89 614551-10
82008 Unterhaching           Web: www.iteratec.de

Sitz und Registergericht der iteratec GmbH: München HRB 113 519
Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel


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--
Dr. Jürgen Lind
iteratec GmbH                Fon: +49 (0)89 614551-44
Inselkammerstrasse 4         Fax: +49 (0)89 614551-10
82008 Unterhaching           Web: www.iteratec.de

Sitz und Registergericht der iteratec GmbH: München HRB 113 519
Geschäftsführer: Klaus Eberhardt, Mark Goerke, Inge Hanschke, Ralf Menzel


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