Can I apply multiple predicates to an NSFetchRequest? Would it be better to manually parse my results?

Question

Ok I have a basic iPad app that asks for 5 search/filter criteria from the user. Based on this data, I need to go to my core data db, and pull out any managed objects that fit that criteria. It seems like I need to apply more than one predicate to the same request, is that possible? Or could I just write a really long fancy predicate? With multiple requirements? How should I approach that?

Would it be a good idea to just grab all the entities through the fetch request, and then loop through each array and grab any objects that I find that fit my search criteria?

Please advise!

Answer 1

Yes it's possible. You're looking for compound predicates and here's an example with AND predicates:

NSPredicate *compoundPredicate 
   = [NSCompoundPredicate andPredicateWithSubpredicates:[NSArray of Predicates]];

You can also use notPredicateWithSubpredicates and orPredicateWithSubpredicates depending on your needs.

Link to documentation https://developer.apple.com/documentation/foundation/nscompoundpredicate

Answer 2

Swift 4

let fetchRequest: NSFetchRequest<YourModelEntityName> = YourModelEntityName.fetchRequest()

let fooValue = "foo"
let barValue = "bar"

let firstAttributePredicate = NSPredicate(format: "firstAttribute = %@", fooValue as CVarArg)
let secondAttributePredicate = NSPredicate(format: "secondAttribute = %@", barValue as CVarArg)

fetchRequest.predicate = NSCompoundPredicate(andPredicateWithSubpredicates: [firstAttributePredicate, secondAttributePredicate])

more information about different types of NSCompoundPredicate constructors can be found here