Core data query

Question

V <-->> O <<--> P

I am trying to write the right predicate so that I can get all V entities that have at least one or more O entities that match a certain P entity.

I've tried something like this:

NSPredicate * predicate = [NSPredicate predicateWithFormat:@"SUBQUERY(O, $b, ANY $bs.P == %@).@count > 0", P];

Not working. Obviously I am not thinking about this correctly so far. Any idea how I can get this query done properly?

You should see some useful stuff in the question and answers there. — jrturton, Oct 06 '12 at 15:41
Thanks for the input. Still not sure how to write the predicate. I'll keep reading that question and answers to it you suggested in the meantime to see if I can figure it out. — zumzum, Oct 07 '12 at 03:51

score 2 · Accepted Answer · answered Oct 07 '12 at 04:13

2

Say the relationship in V to O is called os and the relationship from O to P is called p. The syntax for the subquery would be as follows:

   NSPredicate *predicate = [NSPredicate predicateWithFormat:
                              @"SUBQUERY(os, $o, $o.p == %@).@count != 0", pToMatch];

answered Oct 07 '12 at 04:13

salo.dm

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Right on. Thanks. Now I realize how easy this was, I'm still trying to get core data queries down. Thank you. – zumzum Oct 07 '12 at 13:19
Glad it helped. Unfortunately, it's all very badly documented. – salo.dm Oct 08 '12 at 02:08

Core data query

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