Example Login View Model with Firebase

LoginViewModel.swift

//
//  LoginViewModel.swift
//
//  Created by Vasiliy Savchuk on 11/9/16.
//  Copyright © 2016 All rights reserved.
//
// Usage this snippet:
//   let viewModel: LoginViewModel = LoginViewModel()
//
//    @IBAction func signInButtonDidPress(_ sender: Any) {
//        self.viewModel.email = self.loginTextField.text?.trimmingCharacters(in:NSCharacterSet.whitespaces)
//        self.viewModel.password = self.passwordTextField.text?.trimmingCharacters(in:NSCharacterSet.whitespaces)
//
//        if self.viewModel.email != "" && self.viewModel.password != ""  {
//            self.viewModel.loginUser()
//        } else {
//            showAlert(title: "", message: "Please, enter your email and password")
//        }
//    }


import UIKit
import Firebase
import FirebaseAuth

class LoginViewModel: NSObject {
    
    var email : String?
    var password : String?
    
    var completionHandler: ((FIRUser?, NSError?) -> Void)?
    
    //MARK: Methods

    func loginUser() {
            FIRAuth.auth()?.signIn(withEmail: email!, password: password!, completion: { (user, error) in
                if let handler = self.completionHandler {
                    handler(user, error as NSError?)
                }
            })
    }
}