Network Controller

APIController.swift

fileprivate enum ServiceType:String {
    case GET,POST,PUT,DELETE
}

struct APIController:NetworkProtocol {
    func verifyUserLogin(_ req: Loginrequest, completion: @escaping (LoginResponse?, NetworkError?) -> Void) {
        networkRequestResult(urlString: Constants.API_NEW_PATIENT, type: .POST, header: nil, encodingData: req, completion: completion)
    }
}

extension APIController {
    private func networkRequestResult<T:Decodable,Q: Encodable>(urlString: String,type:PIServiceType,header:[String:String]?,encodingData: Q,completion: @escaping  (Result<T,NetworkingControllerError>) -> Void) {

            guard let url = URL(string: Constants.BASE_URL+urlString) else {
                DispatchQueue.main.async { completion(.failure(NetworkingControllerError.invalidRequest)) }
                return
            }
            var request = URLRequest(url: url)
            request.httpMethod = type.rawValue
            request.addValue("application/json", forHTTPHeaderField: "Accept")
            request.addValue("application/json", forHTTPHeaderField: "Content-Type")
        
            if type != .GET {
                do {
                    let jsonBody = try JSONEncoder().encode(encodingData)
                    request.httpBody = jsonBody
                } catch {
                    DispatchQueue.main.async { completion(.failure(NetworkingControllerError.invalidRequest)) }
                    return
                }
            }
            let task = URLSession.shared.dataTask(with: request) { (data,response, err) in
                if let e = err {
                    print("Failed to fetch data:", e.localizedDescription, "Error Description\(e)")
                    DispatchQueue.main.async {
                        completion(.failure(NetworkingControllerError.forwardedError(Error: e)))}
                    return
                }
                if let r = response {
                    let httpresponse = (r as! HTTPURLResponse)
                    print("statusCode \(httpresponse.statusCode)")
                    if httpresponse.statusCode != 200 {
                        DispatchQueue.main.async {
                            completion(.failure(NetworkingControllerError.noDataError))
                        }
                        return
                    }
                }
                guard let data = data else {
                    DispatchQueue.main.async {
                        completion(.failure(NetworkingControllerError.noDataError))}
                    return
                }
                do {
                    let dataReceived = try JSONDecoder().decode(T.self, from: data)
                    DispatchQueue.main.async {
                        completion(.success(dataReceived))
                    }
                    
                } catch let jsonErr {
                    print("page parse failed error \(jsonErr)")
                    DispatchQueue.main.async {
                        completion(.failure(NetworkingControllerError.dataParseError(error: jsonErr)))
                    }
                }
            }
            task.resume()
        }
}

NetworkError.swift

enum NetworkingControllerError:Error {
    case Non200StatusCode
    case invalidRequest
    case NoInternetConnection
    case forwardedError(Error:Error)
    case noDataError
    case apiError(error:NetworkError?)
    case dataParseError(error:Error)
    case customError(title:String?,message:String)
}

ViewController.swift

class ViewController:UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        let loginRequest = Loginrequest(username: "bharath", password: "bharath")
        APIController().verifyUserLogin(loginRequest) { (response, error) in
            if let e = error {
                print("Login API Error \(e.localizedDescription)")
                switch e {
                case .APINotFoundError: break
                case .InputDataError: break
                case .Non200StatusCode: break
                default:
                    break
                }
            } else {
                if let r = response {
                    if r.status ?? false {
                        print("login is success full")
                    }
                }
            }
        }
    }
}