Best way to implement Enums with Core Data

Question

What is the best way to bind Core Data entities to enum values so that I am able to assign a type property to the entity? In other words, I have an entity called Item with an itemType property that I want to be bound to an enum, what is the best way of going about this.

Answer 1

You'll have to create custom accessors if you want to restrict the values to an enum. So, first you'd declare an enum, like so:

typedef enum {     kPaymentFrequencyOneOff = 0,     kPaymentFrequencyYearly = 1,     kPaymentFrequencyMonthly = 2,     kPaymentFrequencyWeekly = 3 } PaymentFrequency; 

Then, declare getters and setters for your property. It's a bad idea to override the existing ones, since the standard accessors expect an NSNumber object rather than a scalar type, and you'll run into trouble if anything in the bindings or KVO systems try and access your value.

- (PaymentFrequency)itemTypeRaw {     return (PaymentFrequency)[[self itemType] intValue]; }  - (void)setItemTypeRaw:(PaymentFrequency)type {     [self setItemType:[NSNumber numberWithInt:type]]; } 

Finally, you should implement + keyPathsForValuesAffecting<Key> so you get KVO notifications for itemTypeRaw when itemType changes.

+ (NSSet *)keyPathsForValuesAffectingItemTypeRaw {     return [NSSet setWithObject:@"itemType"]; }