How to convert a Swift dictionary with enum keys to an NSDictionary?

Question

I can't convert a Swift dictionary to an NSDictionary . I'm using a Swift enumerate as the key of my dictionary:

enum StringEnum : String {
    case Lemon = "lemon"
    case Orange = "orange"
}

var swiftDictionary = [StringEnum: AnyObject]()
swiftDictionary[.Lemon] = "string value"
swiftDictionary[.Orange] = 123

When I try to convert it to a NSDictionary with the as keyword:

let objcDictionary: NSDictionary = swiftDictionary as NSDictionary

I get the compiler error:

'[StringEnum : AnyObject]' is not convertible to 'NSDictionary'

Can these types of dictionaries be converted or do I need to loop the Swift dictionary and create an NSDictionary manually?

Answer 1

I think if your dictionary have enum values then you can not convert it to NSDictionary but another way to do that is:

//change the type of your dict to [String: AnyObject]()
var swiftDictionary = [String: AnyObject]()

//you can store rawValue as a key
swiftDictionary[StringEnum.Lemon.rawValue] = "string value"
swiftDictionary[StringEnum.Orange.rawValue] = 123

let objcDictionary = swiftDictionary as NSDictionary  //["lemon": "string value", "orange": 123]

Hope this will help.

Answer 2

None of them ( StringEnum , String , Dictionary ) are obj-c types, therefore you cannot do that implicitly. You definitely need a loop for that.

Answer 3

It is complaint because you cannot save values type to NSDictionary (enums is a value type). You have to wrap it to a NSNumber or any other type.