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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