import UIKit

enum Result<Value> {
    case success(Value)
    case error(Error)
}

class Box<T> {

    let value: T

    init(value: T) {
        self.value = value
    }
}

var result = Result.success(Box(value: "Ahoj"))

switch result {
case .success(let box):
    print(box.value)
case .error(let error):
    print(error.localizedDescription)
}