how to keep a user login even if they close the app? I'm using swift 3, and Firebase - ios

Question

I'm new to coding and to Stack overflow, I'm trying to have a user stay logged in even after they close the app. I also don't want them to always see the login in screen. how do I do i go about keeping the user Login even if they close the app and re-open the app. I'm using Swift 3.0, Xcode 8, and Firebase.
import UIKit
import Firebase
import SwiftKeychainWrapper
class LoginViewController: UIViewController {
#IBOutlet weak var emailField: UITextField!
#IBOutlet weak var pwField: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
let tap: UITapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(LoginViewController.dismissKeyboard))
//Uncomment the line below if you want the tap not not interfere and cancel other interactions.
//tap.cancelsTouchesInView = false
view.addGestureRecognizer(tap)
// Do any additional setup after loading the view.
}
func dismissKeyboard() {
//Causes the view (or one of its embedded text fields) to resign the first responder status.
view.endEditing(true)
}
#IBAction func loginPressed(_ sender: Any) {
guard emailField.text != "", pwField.text != "" else {return}
FIRAuth.auth()?.signIn(withEmail: emailField.text!, password: pwField.text!, completion: { (user, error) in
if let error = error {
print(error.localizedDescription)
}
if user != nil {
let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "TabBarViewController")
self.present(vc, animated: true, completion: nil)
}
})
}
}
Below is my UsersViewController code it has the log-out button
import UIKit
import Firebase
class UsersViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {
#IBOutlet weak var tableview: UITableView!
var user = [User]()
override func viewDidLoad() {
super.viewDidLoad()
retrieveUsers()
}
func retrieveUsers() {
let ref = FIRDatabase.database().reference()
ref.child("users").queryOrderedByKey().observeSingleEvent(of: .value, with: { snapshot in
let users = snapshot.value as! [String : AnyObject]
self.user.removeAll()
for (_, value) in users {
if let uid = value["uid"] as? String {
if uid != FIRAuth.auth()!.currentUser!.uid {
let userToShow = User()
if let fullName = value["full name"] as? String, let imagePath = value["urlToImage"] as? String {
userToShow.fullName = fullName
userToShow.imagePath = imagePath
userToShow.userID = uid
self.user.append(userToShow)
}
}
}
}
self.tableview.reloadData()
})
ref.removeAllObservers()
}
func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableview.dequeueReusableCell(withIdentifier: "userCell", for: indexPath) as! UserCell
cell.nameLabel.text = self.user[indexPath.row].fullName
cell.userID = self.user[indexPath.row].userID
cell.userImage.downloadImage(from: self.user[indexPath.row].imagePath!)
checkFollowing(indexPath: indexPath)
return cell
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return user.count
}
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
let uid = FIRAuth.auth()!.currentUser!.uid
let ref = FIRDatabase.database().reference()
let key = ref.child("users").childByAutoId().key
var isFollower = false
ref.child("users").child(uid).child("following").queryOrderedByKey().observeSingleEvent(of: .value, with: { snapshot in
if let following = snapshot.value as? [String : AnyObject] {
for (ke, value) in following {
if value as! String == self.user[indexPath.row].userID {
isFollower = true
ref.child("users").child(uid).child("following/\(ke)").removeValue()
ref.child("users").child(self.user[indexPath.row].userID).child("followers/\(ke)").removeValue()
self.tableview.cellForRow(at: indexPath)?.accessoryType = .none
}
}
}
if !isFollower {
let following = ["following/\(key)" : self.user[indexPath.row].userID]
let followers = ["followers/\(key)" : uid]
ref.child("users").child(uid).updateChildValues(following as Any as! [AnyHashable : Any])
ref.child("users").child(self.user[indexPath.row].userID).updateChildValues(followers)
self.tableview.cellForRow(at: indexPath)?.accessoryType = .checkmark
}
})
ref.removeAllObservers()
}
func checkFollowing(indexPath: IndexPath) {
let uid = FIRAuth.auth()!.currentUser!.uid
let ref = FIRDatabase.database().reference()
ref.child("users").child(uid).child("following").queryOrderedByKey().observeSingleEvent(of: .value, with: { snapshot in
if let following = snapshot.value as? [String : AnyObject] {
for (_, value) in following {
if value as! String == self.user[indexPath.row].userID {
self.tableview.cellForRow(at: indexPath)?.accessoryType = .checkmark
}
}
}
})
ref.removeAllObservers()
}
#IBAction func logOutPressed(_ sender: Any) {
do {
try FIRAuth.auth()?.signOut()
if FIRAuth.auth()?.currentUser == nil {
// Remove User Session from device
UserDefaults.standard.removeObject(forKey: "uid")
UserDefaults.standard.synchronize()
let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "LoginVC") as! LoginViewController
}
} catch let signOutError as NSError {
// handle logout error
}
}
}
extension UIImageView {
func downloadImage(from imgURL: String!) {
let url = URLRequest(url: URL(string: imgURL)!)
let task = URLSession.shared.dataTask(with: url) {
(data, response, error) in
if error != nil {
print(error!)
return
}
DispatchQueue.main.async {
self.image = UIImage(data: data!)
}
}
task.resume()
}
}

Answer 1

Firebase Auth can handle this for you. Like with Firebase Database, Auth works by setting up listeners. You can listen for an existing user in your App Delegate like so:
final class AppDelegate: UIResponder, UIApplicationDelegate {
private let auth = FIRAuth.auth()
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
auth?.addStateDidChangeListener { [weak self] (_, user) in
if let user = user {
// user is already logged in
} else {
// user is not logged in
}
}
}
}

Answer 2

When the user is successfully logged in, put their UID in UserDefaults to store the session like so:
UserDefaults.standard.set(FIRAuth.auth()!.currentUser!.uid, forKey: "user_uid_key")
UserDefaults.standard.synchronize()
Then, whatever is the first View Controller that your apps loads, check for that key in the viewDidAppear() like this:
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
// Check if the user is logged in
if UserDefaults.standard.object(forKey: "user_uid_key") != nil {
// send them to a new view controller or do whatever you want
}
}
Put the UserDefaults in the success block of the IBAction/Function where you register/login your user like shown below:
FIRAuth.auth()?.signIn(withEmail: email, password: password, completion: { (user, error) in
if user != nil {
// Login success
// Saves User UID to UserDefaults
UserDefaults.standard.set(FIRAuth.auth()!.currentUser!.uid, forKey: "USER_KEY_UID")
UserDefaults.standard.synchronize()
}
else {
// login error
})
Remove the UserDefault when the user logs out:
#IBAction func logoutButtonPressed(sender: UIButton!) {
do {
try FIRAuth.auth()?.signOut()
if FIRAuth.auth()?.currentUser == nil {
// Remove User Session from device
UserDefaults.standard.removeObject(forKey: "USER_KEY_UID")
UserDefaults.standard.synchronize()
let loginVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "LoginVC") as! LoginVC
present("TheVCYouWantToSendTheUserTo", animated: true, completion: nil)
}
} catch let signOutError as NSError {
// handle logout error
}
}
UPDATED:
You forgot to include UserDefaults in your Login func. This is why it gives you an error. Add this to you login IBAction.
#IBAction func loginPressed(_ sender: Any) {
guard emailField.text != "", pwField.text != "" else {return}
FIRAuth.auth()?.signIn(withEmail: emailField.text!, password: pwField.text!, completion: { (user, error) in
if let error = error {
print(error.localizedDescription)
// You forgot to save User UID to UserDefaults here...
UserDefaults.standard.set(FIRAuth.auth()!.currentUser!.uid, forKey: "uid")
UserDefaults.standard.synchronize()
}
if user != nil {
let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "TabBarViewController")
self.present(vc, animated: true, completion: nil)
}
})
}