Ahhh, that makes much more sense now.
In this instance I would say that you might want to re-think the way that
you are implementing equals() in your hibernate objects. Even the hibernate
documentation puts in caveates about object identity (tried to lookup a
reference but couldn't find it in time)...Basically, if you don't provide
alternative equals() logic for cases where your objects aren't yet persisted
you are going to run into this problem a ~lot~. For your case, I would do
something similar (but not exactly ;) ) to this for my objects:
public boolean equals(Object obj) {
if (!obj instanceof Foo)
return false;
Foo foo = (Foo)obj;
if (getId() > 0)
return getId() == foo.getId();
else if (getNumber() /* whatever your 1-10 values are stored in*/ ==
foo.getNumber())
return true;
else
return false;
}
Expecting the For component to be able to handle object equality is a very
high order. Perhaps it ~could~ try and do it based on index value, but even
this would probably spurn 10 more mailing list emails for those scnerios
where other people find ~that~ method non-intuitive ;)
Well, that's my opinion on it anyways. (Your idea about the using the same
ordering on index may have merit though, I'd have to crack open the For
component and double check all of that to confirm, could very well be a
great idea...Hard to say right now)
jesse
On 1/26/06, Chris Conrad <[EMAIL PROTECTED]> wrote:
>
> Hi Jesse,
>
> On Jan 26, 2006, at 11:58 AM, Jesse Kuhnert wrote:
>
> > Hmmm. .
> >
> > I do these sort of things a lot, esp. with hibernate. I've found
> > the For
> > component to incredibly useful, but maybe the identification of
> > objects part
> > could be made more clear?
>
> In this case, however, I'm using the For component before anything
> Hibernate related happens. I'm trying to create a list of empty RSVP
> objects which the user fills in and then, after the user fills them
> in, they are persisted. So I can understand why the For component is
> misbehaving for me; all the RSVP objects in the list are initially
> identical.
>
> > I think the PropertySelectionModel problem could be solved if you
> > used the
> > "BeanPropertySelectionModel" class found in
> > http://tacos.sourceforge.netinstead. It makes turning a list of
> > hibernate objects into the selection
> > model a one-line argument.
>
> I'm sorry, I must not have been clear. I'm not putting anything
> Hibernate related at all in the PropertySelectionModel. My drop down
> box is just a list of numbers from 1 to 10. The user uses that drop
> down to select the number of guests attending. Then, using the
> number they gave, I create a list of RSVP objects. That list of RSVP
> objects (which should all be identical, they have no id because they
> haven't been persisted, they have no name associated with them
> because the user hasn't entered it yet, etc.) is then rendered using
> the For component. And then on rewind, the For component just
> continually updates the first RSVP object in the list because it's
> (from my understanding of the code) trying to intelligently choose
> the correct RSVP object from the List to update. But it's
> impossible, in this use case, for it to make a choice that way
> because all of the RSVP objects are legitimately the same at that
> point. That is why I went and added the hack to make sure all the
> RSVP objects aren't identical, they all have a different id. But the
> id I assign isn't a valid id and I need to reset them back to 0
> before I can persist them to Hibernate. And that needing to set the
> id and then reset it is a code smell which bothers me.
>
> I basically want the For component to work like a regular for loop
> and just update the List one by one. There is no possibility of the
> list having changed or of updating the wrong item in the list.
>
> >
> > Let me know if you try that and still find problems.
>
> Please let me know if I'm still not expressing myself clearly
> regarding what the problem is. And thanks for your extremely quick
> response.
>
> --Chris
>
> >
> > On 1/26/06, Chris Conrad <[EMAIL PROTECTED]> wrote:
> >>
> >> Hello everyone,
> >>
> >> I'm working a tiny little RSVP for a friend. While doing so I found,
> >> what seems to me at least, a very non-intuitive result from the For
> >> component. Basically the behavior I want is:
> >>
> >> 1. The user navigates to the RSVP page and is provided a drop down
> >> box to select the number of people who will be attending the event.
> >>
> >> 2. The user is given a list of text entry boxes (to enter the name of
> >> the guest) and drop downs (to select the meal the guest wants).
> >>
> >> 1 was simple to accomplish though having to create a
> >> PropertySelectionModel is kinda a pain for something this simple.
> >> Where things got hairy is 2. Basically the code flow is: in the
> >> listener for the form submit in #1, I grab the number of guests
> >> attending and set that on the meal selection page. The meal
> >> selection page's pageBeginRender creates a List of x RSVP objects
> >> where x is the number of guests attending. Then the meal selection
> >> page uses a For component to loop through the List of RSVP objects so
> >> that, in the first pass everything is blank and then when the guest
> >> submits, those RSVP objects in the List get filled in with the
> >> details the guest entered.
> >>
> >> Now, what actually happened is the first RSVP object in the list is
> >> continually updated over and the others are never touched. When
> >> tracing through the For components code, it appears to be trying to
> >> match the serialized object saved in the form against the ones in the
> >> List to "intelligently" pick which one to update. But since all of
> >> the RSVP objects were the same to start with, and the For component
> >> doesn't update it's internal mapping after updating an object, it
> >> just ignored everything in the list after the first item. Or, I
> >> guess more accurately, it continually matched the first item in the
> >> List and so it just repeatedly updated that one RSVP object. To work
> >> around this, I needed to set the RSVP's id in the pageBeginRender to
> >> a different value for each RSVP object and then reset them back to 0
> >> just before sending them to Hibernate to persist (if I don't reset
> >> them to 0, Hibernate things it's a detached object and ends up
> >> updating a row instead of adding a new row).
> >>
> >> This work around seems very much like a hack to me. Is there a way
> >> to make the For component do the right thing (i.e. actually iterate
> >> over the array when rewinding instead of assuming it knows what it's
> >> doing)? I did try playing with the match parameter and that
> >> completely breaks everything, none of the objects in the List get
> >> updated. It seems that my use case isn't so terribly strange that it
> >> would be this difficult to accomplish in Tapestry.
> >>
> >> Thanks,
> >> --Chris
> >>
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> >>
>
>
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