Attributes as Swift optional?

Question

Hi,

I have an entity with a Double attribute. It is marked as "optional" -- ie, the checkbox is checked in the Core Data inspector in Xcode. It generates this Swift code in the entity class:

@NSManaged public var height: Double

I was expecting it to be `Double?`. Wouldn't that make more sense? I'd like to differentiate between a purposely set value of 0.0, and a nil (ie, never set). Is this supported? If so, is there a way to make it generate the code that way (with `Double?`), or do I need to turn off code generation and write my own subclass of NSManagedObject for this entity?

(Xcode 8, beta 6)

thanks,

Rob

Core Data

5k

Posted by

rnikander

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Answer 1

You cannot use `Double?` for `@NSManaged` attributes, even if you write your own NSManagedObject class yourself:

property cannot be marked @NSManaged because its type cannot be represented in Objective-C

...is what you get for `@NSManaged public var height: Double?`.

`NSManagedObject` utilizes runtime features of Objective-C, so you cannot have an attribute which cannot be represented in Objective-C.

If you want to make the attribute Optional, you may need to change the type to `Decimal`, or choose `NSNumber` to represent the value.

Posted by

OOPer

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Answer 2

You cannot use `Double?` for `@NSManaged` attributes, even if you write your own NSManagedObject class yourself:

property cannot be marked @NSManaged because its type cannot be represented in Objective-C

...is what you get for `@NSManaged public var height: Double?`.

`NSManagedObject` utilizes runtime features of Objective-C, so you cannot have an attribute which cannot be represented in Objective-C.

If you want to make the attribute Optional, you may need to change the type to `Decimal`, or choose `NSNumber` to represent the value.

Posted by

OOPer

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Attributes as Swift optional?

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