Re: Strange error message

Hmm.  I think you have correctly diagnosed the problem, but the whole thing 
is kind of confusing to me.

In my own case, I am using single-table inheritance, with an abstract root 
entity and entity-based restricting qualifiers for each sub-entity.  I 
followed directions in Apple's docs to do this.

Since it's single-table, EOs in the inheritance hiearchy indeed have unique 
pks.  But you can't tell the entity from the pk. If you just know "pk = 
101", that doens't let you know what entity it's from---EOF can't possibly 
use the pk to differentiate what sub-entity/class a row belongs to.  But 
you can know what entity it's from by the restricting qualifier

Things _seem_ to be working okay. I can do a fetch on the abstract root 
entity, and all my EOs come back of the appropriate concrete 
sub-class.  Everything I'm doing is okay, right?

EOEntity inheritance makes me very nervous in general; I'm hesitantly 
trying it out in a rather simple case to see how/if it works.  But the 
whole thing seems rather fragile.

At 10:59 AM 10/8/2002 -0700, Chuck Hill wrote:
>Ah Ha!  I know the answer.  EOs in an inheritance hierarchy MUST MUST MUST 
>have unique primary keys.  That is the only way that EOF can differentiate 
>which class an object is.  In your case
>
>RootClass ----> EntityA
>           ----> EntityB
>
>No object of EntityA, EntityB (or RootClass if not abstract) can have the 
>same PK.   If EOF fetches an instance of EntityA with a PK of 1000, and 
>then fetches an instance of EntityB with a PK of 1000 it will think 
>(because the EOGlobalID is the same) that the EntityB instance is actually 
>the EntityA instance.
>
>
>Chuck
>
>
>Camille Troillard wrote:
>
>>Hi Chuck,
>>
>>On Tuesday, Oct 8, 2002, at 19:34 Europe/Paris, Chuck Hill wrote:
>>
>>>I've only seen this happen when inheritance was involved which, I 
>>>believe, you said was not.  Very strange.
>>
>>Yes, it seems like it.
>>I didn't explained my problem correctly:
>>I actually said that the entities cannot be casted from one to other.
>>But they have the same root class.
>>I have posted a message to Jonathan on eof mailing list, that details the 
>>steps to reproduce to have the problem.
>>You must have received a copy vie the mailing list manager.
>>
>>Best Regards,
>>Camille
>>
>>
>>>Camille Troillard wrote:
>>>
>>>>Hi Anjo,
>>>>First of all, thank you for the help.
>>>>On Tuesday, Oct 8, 2002, at 18:51 Europe/Paris, Anjo Krank wrote:
>>>>
>>>>>This seems like another case of the problem you had with your PKs for 
>>>>>the reference entities - for which I also have no explanation?
>>>>
>>>>I have more infos about my problem:
>>>>Here are the steps I did to reproduce something "weird".
>>>>1. Create an "ODAgency" object.
>>>>The object has been correctly created in the database (ID: 1000004).
>>>>2. Fetch the "ODAgency" objects.
>>>>Only 2 objects, there should be 3.
>>>>     A.  I don't see the object I just inserted (though it is in the DB).
>>>>     B.  The first one in an ODAgency, the second one is ...  a 
>>>> ODAdvertiser !!!!
>>>>         With ID, guess what ??? ID: 1000004 (same as the newly created 
>>>> advertiser).
>>>>The thing is that is seems that EOF gets confused with PK.
>>>>If two entities raws have the same PK, then I have a problem.
>>>>But I can't tell why ...
>>>>
>>>>>Can you post that model somewhere?
>>>>
>>>>For reason you understand, I'll post you the model privately.
>>>>If someone is willing to help me no problem, as far as I know to who I 
>>>>post the model, then it's ok.
>>>>Thanks again,
>>>>Camille
>>>>_______________________________________________
>>>>EOF mailing list
>>>>[email protected]
>>>>http://www.omnigroup.com/mailman/listinfo/eof
>>>
>>>
>>>
>>>--
>>>
>>>Chuck Hill                                 [email protected]
>>>Global Village Consulting Inc.             http://www.global-village.net
>>>
>>>
>>>
>>>_______________________________________________
>>>EOF mailing list
>>>[email protected]
>>>http://www.omnigroup.com/mailman/listinfo/eof
>
>
>--
>
>Chuck Hill                                 [email protected]
>Global Village Consulting Inc.             http://www.global-village.net
>
>
>
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