Swift: Why ?? can not use for String?-CodePudding

I got this error:

Binary operator '??' cannot be applied to operands of type 'String?' and 'UUID'

here:

Binary operator '??' cannot be applied to operands of type 'String?' and 'UUID'

Why? ?? is for optionals, not?

CodePudding user response：

String and UUID are not the same types, so they cannot be compared.

If you want to compare them, you could get the value of the UUID as a String using the UUID.uuidString property.

let x: String? = nil
let uuid = UUID()

let y: String = x ?? uuid.uuidString

CodePudding user response：

first, get device UDID as a String after that you can compare

let udid = UIDevice.current.identifierForVendor!.uuidString