the added value is that if wicket detects that the set is a noop
because the objects are the same it doesnt need to create a new
version of the page.
-igor
On Wed, Jul 21, 2010 at 8:25 AM, Joseph Pachod <j...@thomas-daily.de> wrote:
> hi
>
> I was surprised to see, in Component.setDefaultModelObject(), the following
> code:
> // Check whether this will result in an actual change
> if (!getModelComparator().compare(this, object))
> {
> modelChanging();
> model.setObject(object);
> modelChanged();
> }
>
> getModelComparator() being down to, by default, a simple equals between the
> present model object and the object to set.
>
> This setDefaultModelObject is called from updateModel of FormComponent.
>
> Why is that ?
>
> AFAIK, it brings quite some disadvantages:
> - adds quite some cost (equals test can be quite expensive, and are always
> more than just assigning a reference)
> - if equals isn't properly implemented, can be either meaningless (default
> equals being different instances are never equals even if logically equal)
> or not appropriate (in entities, my equals is based on the id, which when
> editing obviously causes an issue here)
> - IModel implementations don't behave like that (setObject for a
> PropertyModel or a Model don't check for non equality)
>
> Yet I don't see any added value...
>
> In the end, I see potential for misbehavior or unexpected one and no added
> value.
>
> So, why it it this way ?
>
> thanks in advance
> ++
>
> --
> Joseph Pachod
> IT
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