Declare Swift struct which becomes enum in Objective-C?

Question

Approximate code I need to write

@objc(OCSomeEnum)
enum SomeEnum: Int {
  case c1
  case c2
  ...
}

extension UnitySSPPlacementType { //available in swift only
  ...
}

I want to use some multiple values from this enum:

@objc(OCSomeClass)
class SomeClass: NSObject {
  @objc
  init(cases: [SomeEnum]) {
    ...
  }
}

Problem

@objc conflicts with [SomeEnum] (it understands SomeEnum only).

Note: there are similar questions but they are all about how to use swift enum one value inside objc (or vice versa). No one answers how to work with multiple values in boths languages simultaneously.

The only clue I found out:

https://developer.apple.com/documentation/uikit/uiview/1622451-animatewithduration?language=objc https://developer.apple.com/documentation/uikit/uiview/1622451-animate

Swift: struct AnimationOptions

Objective-C:

typedef enum UIViewAnimationOptions : NSUInteger {
    ...
} UIViewAnimationOptions;

But how to declare custom Swift struct which becomes enum in Objective-C?

Solution

According to @MartinR advice:

@objc
convenience init(cases: Array<Int>) {
  let pCases = cases.map { SomeEnum(rawValue: $0)! }
  self.init(cases: pTypes)
}

init(cases: [SomeEnum]) { ... }

Bridging an array of enums from Swift to Objective-C

The problem is that an *array* of enums is not bridged to Objective-C. See https://stackoverflow.com/q/30453961/1187415 for an explanation and a possible workaround. — Martin R, Jul 13 '22 at 14:17
You can declare an enum in ObjC with the `NS_OPTIONS` macro and it will import into swift as a struct conforming to `OptionSet` but the other direction doesn't work — dan, Jul 13 '22 at 14:31
the solution from MartinR is ok, writing enum in ObjC is not suitable for my case — Вячеслав Герчиков, Jul 14 '22 at 08:15

Timmy · Answer 1 · 2022-07-14T11:45:37.173

0

Enums in Objective-C are values which is different than Swift. To complement this difference, make your enum conform to RawRepresentable. After conformance, SomeEnum.c1 will be of type Int having a value equal to its rawValue.

Here's an Example:

enum SomeEnum: RawRepresentable {
    case c1, c2
    var rawValue: Int {
        switch self {
        case .c1:
            return 1
        case .c2:
            return 2
        }
    }
    init?(rawValue: Int) {
        switch rawValue {
        case 1:
            self = .c1
        case 2:
            self = .c2
        default:
            return nil
        }
    }
}

@objc(OCSomeClass)
class SomeClass: NSObject {
    @objc init(cases: [SomeEnum.RawValue]) {
    }
}

let someProperty = SomeClass(cases: [SomeEnum.c1.rawValue])

Edit:

Updated Class

@objc(OCSomeClass)
class SomeClass: NSObject {
    @objc convenience init(cases: [SomeEnum.RawValue]) {
        self.init(enumCases: cases.map({SomeEnum(rawValue: $0)}))
    }
    init(enumCases: [SomeEnum?]) {
        
    }
}

let someProperty = SomeClass(cases: [SomeEnum.c1.rawValue])

edited Jul 14 '22 at 11:45

answered Jul 13 '22 at 12:36

Timmy

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Could you please post a concrete example? I added `RawRepresentable` to my enum but it still writes "Method cannot be marked @objc because the type of the parameter cannot be represented in Objective-C" – Вячеслав Герчиков Jul 13 '22 at 12:44
1

Iirc, only integer backed enums can be exposed to objective c, because that’s the only kind it supports. – Alexander Jul 13 '22 at 13:19
add `init(cases: [SomeEnum])` and call it from your `@objc init` please and I will confirm your answer – Вячеслав Герчиков Jul 14 '22 at 08:18
Please confirm if my edit is what you want – Timmy Jul 14 '22 at 11:45

Declare Swift struct which becomes enum in Objective-C?

1 Answers1