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I have a to-many relationship in my data model, and I’d like to get all the objects that have no corresponding objects in the relationship. For example:
Customer -> Purchases
I want to get all Customers that have 0 Purchases.
I’ve read somewhere that I could use “Purchases[SIZE] = 0”, but this gives me an unsupported function expression error, which I think means it doesn’t work with a SQLite backing store (which I don’t want to switch from, due to some performance constraints).
Any ideas?
I found the answer elsewhere, here it is for future use. Tested on iPhone OS 3.0.
[NSPredicate predicateWithFormat:@”Purchases.@count == 0″];