Not much time to properly respond, but make sure to override equals and hashcode on the objects so that to *value-identical* instances are treated as the same instance. Usually with JPA you're not looking for object equivalence but value equivalence.
Derek On Fri, Jan 9, 2009 at 5:18 PM, Charles F. Munat <c...@munat.com> wrote: > > I'm trying to create a way for users to add multiple "worm" objects to > an "apple" object in a many-to-many relationship, so I could access them > as apple.worms (which returns a Java set, it seems). > > The first hassle was trying to find the best interface. I rejected a > multi-select box because people have a hell of a time with it, > especially on an edit where if you forget to hold the Control (Command) > key down while selecting, you could delete the previously selected objects. > > I also rejected a two-box solution where you use left and right arrows > to move from the pool of objects to the attached objects (or back > again). This also is difficult for some people and a pain to implement. > > Instead, I like the idea of a simple single item select menu and an Add > button using AJAX to add the worm to the apple. To make this simpler, by > form is multi-page. You create an apple first, then on the next page you > can add worms (and other m-m things). So the AJAX always has a > persistent apple to which to add the worms. > > Better ideas welcome, but this is sufficient. > > The worms then have a Remove button next to them which permits the > association between them and the apple to be deleted. > > (I also plan a pop-up form that allows one to add new worms from within > the apple form.) > > So now I want to populate the drop down menu with the names of those > worms *not already associated with the apple*. My first attempt was by > pulling down a set of all the worms (there won't be many) and stuffing > it in a val. Then I made a list of all the worms associated with the > apple. Then -- heh, heh -- I cleverly subtracted the latter from the > former to get the unused worms. > > Except that it didn't work, of course. They may be the same worms, but > the system sees them as two different objects for some reason. Now it's > getting complicated. Do I have to compare them on the ID? > > There must be a better way. > > So, has anyone done anything like this using JPA/Hibernate and Lift, or > am I on my own? > > Thanks! > > Chas. > > P.S. As usual, I need this like yesterday, so I'll continue working on > it... > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Lift" group. To post to this group, send email to liftweb@googlegroups.com To unsubscribe from this group, send email to liftweb+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/liftweb?hl=en -~----------~----~----~----~------~----~------~--~---
