extension_subscript.swift

extension CreditCard {
    
    subscript(index: Int) -> String? {
        switch index {
        case 0:
            return number
        case 1:
            return date
        case 2:
            return name
        case 3:
            return ccv
        default:
            return nil
        }
    }
    
}

let subscriptCard = CreditCard(number: "4111 0000 2345 0000", date: "03/20", ccv: "243")
print("card number: \(String(describing: subscriptCard[0]))")
// Optional("4111 0000 2345 0000")
print("card date: \(String(describing: subscriptCard[1]))")
// Optional("03/20")
print("card name: \(String(describing: subscriptCard[2]))")
// Optional("")
print("card ccv: \(String(describing: subscriptCard[3]))")
// Optional("243")