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s.rottem
 Post subject: Bidirectional mapping using List?
PostPosted: Fri Dec 09, 2005 12:27 pm 
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I found the following statement in the documentation:

Quote:
Please note that Hibernate does not support bidirectional one-to-many associations with an indexed collection (list, map or array) as the "many" end, you have to use a set or bag mapping.


Can anyone explain WHY? I want to have objectA have an ordered collection of objectB but be able to find the parent objectA of any given objectB. Is this not possible? Or have I misunderstood the statement?

Symon.
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Nels_P_Olsen
 Post subject:
PostPosted: Fri Dec 09, 2005 1:02 pm 
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Yes, I'd also like to hear clarification on this. I've set up a one-to-many using <map>, where the elements have a reference back to their "parent", and simple testing (add parent, add elements, delete elements) revealed no issues ...
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sergey
 Post subject:
PostPosted: Fri Dec 09, 2005 8:13 pm 
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The reason is that the child object doesn't know its index in the parent's collection, so it can't update its table record correctly. In Hibernate 3 they solved it, I believe, by traversing all collections known to the session and looking in them for the object, but Hibernate 2.1 (and NH) doesn't do it.
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s.rottem
 Post subject:
PostPosted: Sat Dec 10, 2005 5:24 am 
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So if the child's reference to the parent was never updated there wouldn't be a problem?

Symon.
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sergey
 Post subject:
PostPosted: Sat Dec 10, 2005 6:41 am 
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I think there won't be a problem, but I never tried :)
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Nels_P_Olsen
 Post subject:
PostPosted: Sat Dec 10, 2005 12:01 pm 
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The child doesn't know it's index in the collection? I'm confused. <map> gives you an IDictionary. The index is a child property used for the DictionaryEntry key (or at least I set it up that way). :?:
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sergey
 Post subject:
PostPosted: Sat Dec 10, 2005 5:28 pm 
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All right, but how is NHibernate supposed to know this? And what about cases where there isn't such a property in the child?
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