How to use binary flags in Core Data?

Question

I have an int32 attribute in a Core Data database. I use this int as an enum bit field.

Is it possible to create a NSPre

Answer 1

Here is one example / application of this technique.

Say you have a NSManagedObject that has an integer attribute with the keypath "typeValue".

Somewhere in your code define a bitwise enumeration:

typedef enum SomeType {
    SomeTypeValueOne = 0x1,
    SomeTypeValueTwo = 0x2,
    SomeTypeValueThree = 0x4
} SomeType;

Now to query for managed objects that are of type say One or Three but not Two, do the following:

SomeType valueOneOrThree = SomeTypeValueOne | SomeTypeValueThree;

NSPredicate *someTypePredicate = [NSPredicate predicateWithFormat:@"(typeValue & %i) == typeValue", valueOneOrThree];

// construct NSFetchRequest as normal with predicate...