alamofire-evolution-now.swift

struct APIError {
    let code: Int
    let message: String
}

struct UserListAPIResponseData {
    let users: [User]
    /// This is a list of users, we might have pagination information, thus struct comes in handy in holding that information
}

enum UserListAPIResponse {
    case Success(UserListAPIResponseData)
    case Fail(APIError) /// Error code, Error message
}

func getUsers(complete: @escaping (UserListAPIResponse) -> ()) -> Request {
    return alamoFireManager
        .request("https://myserver.com/",
                 method: .get,
                 parameters: nil,
                 encoding: JSONEncoding.default,
                 headers: nil)
        .validate(statusCode: 200..<500)
        .responseJSON(completionHandler: { (response) in
            switch response.result {
            case .success(let data):
                switch response.response?.statusCode {
                case 200, 204:
                    /// Handle success, parse JSON data
                    do {
                        let users = try JSONDecoder().decode([Users].self, from: JSONSerialization.data(withJSONObject: data))
                        complete(.Success(UserListAPIResponseData(users: users)))
                    } catch let error {
                        /// Handle json decode error
                        complete(.Fail(APIError(code: -1, message: "we ran into error")))
                    }
                case 429:
                    /// Handle 429 error
                    complete(.Fail(APIError(code: 429, message: "we ran into error")))
                default:
                    /// Handle unknown error
                    complete(.Fail(APIError(code: -1, message: "we ran into error")))
                }
            case .failure(let error):
                /// Handle request failure
                complete(.Fail(APIError(code: 0, message: "we ran into error")))
            }
        })
}