NSPredicate - filtering values based on a BOOLEAN stored value

Question

I have a core data model object called Entry. In this I have an attribute IsFavorite.

I would like to use an NSPredicate to filter the results of my NSFetchedResultsCont

Answer 1

swift 3 version worked great for me:

 let predicate = NSPredicate(format: "isFriend == %@" ,NSNumber(booleanLiteral: false))

following @scipilot answer the bool shouldn't be an optional. thanks for that!

Answer 2

Interestingly if you "know" which one you want, you can just have:

let p = NSPredicate(format: "showMe == true")

example,

let r = NSFetchRequest<NSFetchRequestResult>(entityName: "CDThing")
let p = NSPredicate(format: "showMe == true")
r.predicate = p

You would do this for things like "subscribed", "new" etc.

Answer 3

on iOS 10, xcode 9.0, looking for a core data managedObject with Boolean NO attribute:

[NSPredicate predicateWithFormat:@"attributeName == nil"]

Answer 4

This isn't really specific to NSPredicate... Whenever you have %@ in a format string, the corresponding value must be a pointer to an object, and BOOL doesn't qualify. So instead of passing YES, pass [NSNumber numberWithBool: YES].

---

In newer versions of Xcode and the SDKs than when I originally wrote the answer, you can use @YES instead of [NSNumber numberWithBool: YES].

Answer 5

From Apple's documentation:

Boolean Values

You specify and test for equality of Boolean values as illustrated in the following examples:

NSPredicate *newPredicate =
    [NSPredicate predicateWithFormat:@"anAttribute == %@", [NSNumber numberWithBool:aBool]];
NSPredicate *testForTrue =
    [NSPredicate predicateWithFormat:@"anAttribute == YES"];

However, something that caught me out:

Be sure to untick the Optional entity attribute and set a Default Value of YES or NO, otherwise the column will be empty (null?) and the above predicates will not match rows which are not explicitly set.

I used the great app sqllitebrowser to diagnose this one, by looking at the resulting simulator database.

Answer 6

If you know you're looking for a YES (and therefore don't need to switch between YES or NO in different situations), this worked for me:

[NSPredicate predicateWithFormat:@"isFavorite == 1"]