NSPredicate by NSManagedObject for many-to-one lookups

I've got the scenario with two NSManagedObjects, Arm and Person. Between them is a many-to-one relationship Person.arms and inverse Arm.owner.

I'd like to write a simple NSPredicate where I've got the NSManagedObject *arm and I'd like to fetch the NSManagedObject *person that this arm belongs to. I could mak开发者_如何学Goe a textual representation and look for that, but is there a better way where I can look it up by identity? Something like this perhaps?

NSEntityDescription *person = [NSEntityDescription entityForName:@"Person" inManagedObjectContext:MOC];
NSPredicate *personPredicate = [NSPredicate predicateWithFormat:@"%@ IN arms", arm];

Cheers

Nik

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I've got the scenario with two NSManagedObjects, Arm and Person. Between them is a many-to-one relationship Person.arms and inverse Arm.owner.

I'd like to write a simple NSPredicate where I've got the NSManagedObject *arm and I'd like to fetch the NSManagedObject *person that this arm belongs to.

That would be myArm.owner. No predicate needed; this is what the inverse relationship is for.