(Swift) Result<Success, Failure> 타입

 

네트워크를 공부하며 알게된 Result 타입은, success 혹은 failure 결과를 나타내준다.

 

enumeration (열거형) Result type

 

@frozen public enum Result<Success, Failure> where Failure : Error {

    /// A success, storing a `Success` value.
    case success(Success)

    /// A failure, storing a `Failure` value.
    case failure(Failure)

    ....
    
}

 

 

 

 

사용 예시) 

struct UserProfile: Codable {
    let loginId: String
    let avatarUrl: String
    let followers: Int
    let following: Int
    
    enum codingKeys: String, CodingKey {
        case loginId = "login"
        case avatarUrl = "avatar_url"
        case followers
        case following
    }
}

final class NetworkService {
    let session: URLSession
    
    init(configuration: URLSessionConfiguration) {
        session = URLSession(configuration: configuration)
    }
    
    func fetchProfile(userName: String, completion: @escaping (Result<UserProfile, Error>) -> Void {
        let urlString = "https://xxxx.xxxxx.com/users/\(userName)"
        let url = URL(string: urlString)!
        
        let task = session.dataTask(with: url) { data, response, error in
            if let error = error { // nil이 아닌경우, 즉 error에 값이 있는 경우
                completion(.failure(error))
                return
            }
            
            if let response = response as? HTTPURLResponse,
                !(200..<300).contains(response.statusCode) {
                completion(.failure(error))
                return
            }
            
            guard let data = data else { // data is optional
                completion(.failure(error))
                return
            }
            
            do {
                let decoder = JSONDecoder()
                let profile = try decoder.decoder(UserProfile.self, from: data)
                completion(.success(profile))
            } catch let error {
                completion(.failure(error))
            }
        }
        task.resume()
    }
}

let networkService = NetworkService(configuration: .default)

// NetworkService 객체 사용 기본형
// networkService.fetchProfile(userName: "aaa", completion: (Result<UserbProfile, any Error>) -> Void)

networkService.fetchProfile(userName: "hortenssiaa") { result in
    // result 는 Result<UserProfile, Error> 타입이므로, success / failure 두가지 case로 나뉜다
    switch result {
    case .success(let profile):
        print("[Profile]: \(profile)")
    case .failure(let error):
        print("[Error]: \(error)")
    }
}

 

 

 

 

 

 

https://hortenssiaa.tistory.com/35

(Swift) @frozen