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I have a mixed-language project, Objective C and Swift, in XCode 6.

Singleton.h

#import <Foundation/Foundation.h> enum { enum_A = 0, enum_B, enum_C, enum_D, enum_E, enum_F, enum_G, } enums; @interface Singleton : NSObject + (id)sharedSingleton; @end

Singleton.m

// Nothing's special in this file #import "Singleton.h" static Singleton *shared = nil; @implementation Singleton - (id)init { self = [super init]; if (self) { } return self; } #pragma mark - Interface + (Singleton *)sharedSingleton { static dispatch_once_t pred; dispatch_once(&pred, ^{ shared = [[Singleton alloc] init]; }); return shared; } @end

ViewController.swift

import UIKit class ViewController: UIViewController { let singleton = Singleton.sharedSingleton() as Singleton override func viewDidLoad() { super.viewDidLoad() // Do any additional setup after loading the view, typically from a nib. let n = NSNumber(char: enum_E) // ERROR HERE!!! } override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() // Dispose of any resources that can be recreated. }

}

(Of course I had to setup bridging header file, having #import "Singleton.h" added).

The ERROR is:

Cannot invoke 'init' with an argument list of type '(char: Int)'

It's strange that Swift can still recognize enum_E (I see it colorized in blue) but still pops up this error. I tried (char)enum_E but still no luck.

Do you have any ideas?

Thanks,

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  • Have you tried NSNumber(int: enum_E)? Commented Dec 12, 2014 at 10:06

1 Answer 1

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Okay, apparently there actually is a difference between enums created in Objective-C and Swift. I assumed there was no difference, thus I only tested my approach in a Swift Playground.

enum created in Swift

// UInt32 used to have the same underlying type in both examples enum TestEnum : UInt32 { case A, B, C } var x = NSNumber(unsignedInt: TestEnum.C.rawValue) // x == 2

To get the raw value from an enum value in Swift, you have to explicitly transform the enum value into the raw value. This can be done by adding .rawValue to your enum value.

enum created in Objective-C

Objective-C

enum TestEnum { A = 0, B = 1, C = 2 };

Swift

let x : TestEnum = C var number = NSNumber(unsignedInt: C.value) // alternative: x.value println("the number is \(number)") // Outputs: the number is 2

The difference to the Swift enums seems to be that you have to use .value instead of .rawValue and you can not prefix them with the type. The raw type in this case is UInt32.

Tested in Xcode 6.1.1, iOS SDK 8.1, iOS Simulator 8.1

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4 Comments

Thanks for your reply, Nero. I tried your approach but XCode alerts: Int does not have a member named 'rawValue'. I guess it's because my enum is defined in Objective C, not in Swift? Reference: link, Raw Value section.
@quanguyen I assumed there was no difference. I updated my answer with code using an enum actually defined in Obj-C.
Thanks a lot for your help. It simply works perfectly! However, in my code, the definition of enums is enum {...} enums while yours is enum enums {...}. If I take your code, Swift knows what enums is and works greatly as mentioned above; but if I take mine, it does not know my enums. I wonder if there is a way to use my code but Swift can still recognize my defined enums. Thanks
@quanguyen One can define enums in a lot of ways, so this would be better suited for a new question. With leaving out TypeName in enum TypeName {...} instanceName; you basically define a new variable named instanceName with the type enum {...}, and the type itself does not get a name. Doing a quick search, I found this reference for C++, which should be quite similar to Obj-C enums, as both languages inherited them from C. Or maybe you can find an existing question here on StackOverflow.

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