Re: Why is Component.setDefaultModelObject() checking for equality before setting ?
Igor Vaynberg wrote: 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. ok, makes more sense :) I was quite a surprised though, I had not heard of it at all even read all these wicket books and using wicket for quite some time. Yet making this corner stuff more visible is probably hard. thanks for your answer anyway ++ joseph - To unsubscribe, e-mail: users-unsubscr...@wicket.apache.org For additional commands, e-mail: users-h...@wicket.apache.org
Why is Component.setDefaultModelObject() checking for equality before setting ?
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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Re: Why is Component.setDefaultModelObject() checking for equality before setting ?
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
THOMAS DAILY GmbH
Adlerstraße 19
79098 Freiburg
Deutschland
T + 49 761 3 85 59 506
F + 49 761 3 85 59 550
E joseph.pac...@thomas-daily.de
www.thomas-daily.de
Geschäftsführer/Managing Directors:
Wendy Thomas, Susanne Larbig
Handelsregister Freiburg i.Br., HRB 3947
Registrieren Sie sich unter https://www.thomas-daily.de/user/sign-in für die
TD Morning News, eine kostenlose Auswahl aktueller Themen aus TD Premium,
morgens ab 9:15 in Ihrer Mailbox.
Aktuelle Presseinformationen für die TD Morning News und TD Premium nimmt
unsere Redaktion unter redakt...@thomas-daily.de entgegen.
Redaktionsschluss für die TD Morning News ist täglich um 8:45.
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the TD Morning News, a selection of the latest topics from TD Premium,
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Morning News and TD Premium at redakt...@thomas-daily.de. The editorial
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