Swift: Storing states in CoreData with enums

Question

I want to store an enum state for a managed object within CoreData

enum ObjStatus: Int16 {
    case State1 = 0
    case State2 = 1
    case State3 = 3
}

class StateFullManagedObject: NSManagedObject {
    @NSManaged var state: Int16
}

The last step would be converting the state var of StateFullManagedObject to ObjStatus for direct comparison, which isn't working for me. For example, I can't use the == operator between and Int16 and the Int16 enum. The compile time error I get is

Int16 is not convertible to 'MirrorDisposition'

. See the conditional below:

var obj: StateFullManagedObject = // get the object

if (obj.state == ObjStatus.State1) { // Int16 is not convertible to 'MirrorDisposition'

}

How can I compare/assign between an Int16 and an enum?

Answer 1

You can declare your enum as @objc. Then it all automagically works. Here's a snippet from a project I'm working on.

// Defined with @objc to allow it to be used with @NSManaged.
@objc enum AgeType: Int32
{
    case Age                = 0
    case LifeExpectancy     = 1
}

/// The age type, either Age or LifeExpectancy.
@NSManaged var ageType: AgeType

In the Core Data model, ageType is set to type Integer 32.

Answer 2

You can extract raw Int16 value with .rawValue property of ObjStatus.

// compare
obj.state == ObjStatus.State1.rawValue

// store
obj.state = ObjStatus.State1.rawValue

But you might want to implement stateEnum accessor for it:

class StateFullManagedObject: NSManagedObject {
    @NSManaged var state: Int16
    var stateEnum:ObjStatus {                    //  ↓ If self.state is invalid.
        get { return ObjStatus(rawValue: self.state) ?? .State1 }
        set { self.state = newValue.rawValue }
    }
}

// compare
obj.stateEnum == .State1

// store
obj.stateEnum = .State1

// switch
switch obj.stateEnum {
case .State1:
    //...
case .State2:
    //...
case .State3:
    //...
}