How can i separate my networking code from my ViewController

Question

I'm using Alamofire for make a post request at the moment. I first built it in the ViewController and worked. But then i'm trying to separate it by building it in another class . I use a singleton and still works when i call in the ViewController . The only problem is after the status coming back a success i am trying to instantiate the another ViewController when the user logs in. I don't want to do it in the networking class, i would like to do it inside my ViewController. How can i achieve this?

enum Status: Int {
    case Success = 200
    case Failure = 401
}

enum HTTPMethod: String {
    case Post = "POST"
    case Get = "GET" 
}

enum APIKey: String {
    case value = "somevalueeeeeeeee"
    case key = "somekeyyyyyyyyyyyyyy"
}

import Foundation
import Alamofire
import UIKit

class NetworkManager {
    static let shared = NetworkManager()

    func makePostRequest(url: URL, params: Parameters, headers: HTTPHeaders, credential: URLCredential) {
        Alamofire.request(url, method: .post, parameters: params, headers: headers).authenticate(usingCredential: credential)
            .responseJSON { response in
                print(response)
                let status = response.response?.statusCode
                switch status {
                case Status.Success.rawValue:
                    print("I would like to instantiate my viewcontroller here")
                case Status.Failure.rawValue:
                    print("Bad Request")
                default:
                    break
                }
        }
    }
}

import UIKit
import Alamofire

class LoginViewController: UIViewController {
    @IBOutlet weak var emailTextField: UITextField!
    @IBOutlet weak var passwordTextfield: UITextField!

    private func login() {
        guard let userName = emailTextField.text else { return }
        guard let passWord = passwordTextfield.text else { return }

        let params: Parameters = [
            "username": userName,
            "password": passWord
        ]
        guard let url = URL(string: URLS.url.rawValue) else { return }
        let headers = [APIKey.key.rawValue: APIKey.value.rawValue]
        let credential = URLCredential(user: userName, password: passWord, persistence: .forSession)

        NetworkManager.shared.makePostRequest(url: url, params: params, headers: headers, credential: credential)
    }

    @IBAction func onLoginTapped(_ sender: UIButton) {
            login()
        }
    }

Answer 1

Add completion block to your function :

func makePostRequest(url: URL, params: Parameters, headers: HTTPHeaders, credential: URLCredential, completion:@escaping(Bool)->()) {
    Alamofire.request(url, method: .post, parameters: params, headers: headers).authenticate(usingCredential: credential)
        .responseJSON { response in
            print(response)
            let status = response.response?.statusCode
            switch status {
            case Status.Success.rawValue:
                print("I would like to instantiate my viewcontroller here")
                completion(true)
                break
            case Status.Failure.rawValue:
                print("Bad Request")
                completion(false)
                break
            default:
                break
            }
    }
}

And call it like this from ViewController:

NetworkManager.shared.makePostRequest(url: URL, params: Parameters, headers: HTTPHeaders, credential: "") { (success) in
    if success {

    } else {

    }
}

Answer 2

You can pass the completion handler to your controller from Network manager class.

 func makePostRequest(url: URL, params: Parameters, headers: HTTPHeaders, credential: URLCredential, completion:@escaping (Result<Any>)->()) {
        Alamofire.request(url, method: .post, parameters: params, headers: headers).authenticate(usingCredential: credential)
            .responseJSON { response in
                print(response)
                completion(response.result)
                let status = response.response?.statusCode
                switch status {
                case Status.Success.rawValue:
                    print("I would like to instantiate my viewcontroller here")
                     completion(response.result)
                    break
                case Status.Failure.rawValue:
                    print("Bad Request")
                     completion(response.result)
                    break
                default:
                    break
                }
        }
    }

And now You can call this function as like below

  NetworkManager.shared.makePostRequest(url: url, params: , headers: param, credential: credential, completion: { (response) in
         if result.isSuccess, let json = result.value {
            // Use json variable to handle json
        } else {
            self.showAlert(R.string.keys.somethingWentWrong())
        }
   })