ResultType.swift

import Foundation

// Result type is enum with two cases, success and error.
// Introduced in swift 5

enum ScoreboardError: Error {
    case serverDown
    case badURL
    case unknown
}

struct Scoreboard {
    let score: Int
}

func fetchScoreBoard(gameID: Int,
                     completion: @escaping ((Result<Scoreboard, ScoreboardError>) -> Void)) {
    // faking network request...
    DispatchQueue.main.asyncAfter(deadline: .now() + 5) {
        let score = Int.random(in: 1...100)
        if score >= 35  {
            completion(.success(Scoreboard(score: score)))
        } else {
            completion(.failure(.unknown))
        }
    }
}

fetchScoreBoard(gameID: 1) { result in
    switch result {
    case .success(_):
        print("congratulations you won!!!")
    default:
        print("Better luck next time :(")
    }
}