如何在Swift枚举中打印关联值？

Question

I'm looking for a way to print associated values of enumetations in Swift. ie. following code should print "ABCDEFG" for me but it doesn't.

enum Barcode {
    case UPCA(Int, Int, Int, Int)
    case QRCode(String)
}

var productCode = Barcode.QRCode("ABCDEFG")
println(productCode)

// prints (Enum Value)

Reading the answers to this stackoverflow question, which is related to printing raw values of enumerations, I tried following code but it gives me an error

enum Barcode: String, Printable {
    case UPCA(Int, Int, Int, Int)
    case QRCode(String)
    var description: String {
        switch self {
            case let UPCA(int1, int2, int3, int4):
                return "(\(int1), \(int2), \(int3), \(int4))"
            case let QRCode(string):
                return string
        }
    }
}

var productCode = Barcode.QRCode("ABCDEFG")
println(productCode)

// prints error: enum cases require explicit raw values when the raw type is not integer literal convertible
//        case UPCA(Int, Int, Int, Int)
//             ^

Since I'm new to Swift I can't understand what error message is about. Can someone know if it is possible or not.

Answer 1

The problem is that you added an explicit raw type to your Barcode enum— String . Declaring that it conforms to Printable is all you need:

enum Barcode: Printable {
    case UPCA(Int, Int, Int, Int)
    case QRCode(String)
    var description: String {
        // ...
    }
}

The compiler's complaint is that you didn't specify raw values with your non-integer raw value type, but you can't do that with associated values anyway. Raw string values, without associated types, could look like this:

enum CheckerColor: String, Printable {
    case Red = "Red"
    case Black = "Black"
    var description: String {
        return rawValue
    }
}