Accessing UserDefaults in Swift from other viewControllers - ios

Question

In my application, I use UserDefaults to store the user's login status (whether they are logged in or not), and their username. It works fine in that when I login, close the app, and open it again my app skips the login page and recognizes that I am already logged in. Although, I am now trying to install a logout button to a separate viewController. When clicked, this logout button needs to 1.) Reset UserDefaults.loginStatus to "False" 2.) Reset UserDefaults.username to nil 3.) Perform a segue to the login page.
Here is the related code from my ViewController.swift file. This is the first viewController which controls the loginPage.
import UIKit
import Firebase
let defaults = UserDefaults.standard
class ViewController: UIViewController {
func DoLogin(username: String, password: String) {
//I Am not including a lot of the other stuff that takes place in this function, only the part that involves the defaults global variable
defaults.setValue(username, forKey: "username")
defaults.setValue("true", forKey: "loginStatus")
defaults.synchronize()
self.performSegue(withIdentifier: "loginToMain", sender: self) //This takes them to the main page of the app
}
override func viewDidLoad() {
super.viewDidLoad()
if let stringOne = defaults.string(forKey: "loginStatus") {
if stringOne == "true" { //If the user is logged in, proceed to main screen
DispatchQueue.main.async
{
self.performSegue(withIdentifier: "loginToMain", sender: self)
}
}
}
}
Below is my code in SecondViewController.swift, particularly the logout function.
import UIKit
import Firebase
class SecondViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
if let username = defaults.string(forKey: "username") {
checkAppSetup(username: username) //This is an unrelated function
//I included this because this works fine. Proving that I am able to read the defaults variable fine from this other viewController
}
}
#IBAction func logout(_ sender: Any) {
defaults.setValue("false", forKey: "username")
defaults.setValue("false", forKey: "loginStatus")
defaults.synchronize()
performSegue(withIdentifier: "logoutSegue", sender: nil)
}
When the logout function is run, the segue performs fine but the default values do not change. Can someone explain why and what I can do to get around this?
**Side note, I am not actually going to set the defaults to "false" and "false". That is just temporary for while I am debugging this issue.

Answer 1

Several things.
You should be using set(_:forKey:) and object(_:forKey) to read and write key/value pairs to defaults, not setValue(_:forKey). (Your use of defaults.string(forKey: "loginStatus") is correct, however.)
You should probably be writing a nil to the userName key:
defaults.set(nil, forKey: "username")
And your logout IBAction should almost certainly be setting loginStatus to false, not true.
Try changing those things.
Also, there is no reason to call synchronize unless you are terminating your app in Xcode rather than pressing the home button on the device/simulator in order to let it exit normally.

Answer 2

Hey i used the exactly same concept recently :
1) In your initial view, in the viewDidLoad() , check whether somebody is already logged in or not, and only one user can be logged in one device at a time, so we check like
let defaults = UserDefaults.standard
if defaults.object(forKey: "userName") != nil && defaults.object(forKey: "userPassword") != nil
{
let loginObject = self.storyboard?.instantiateViewController(withIdentifier: "YourSecondViewController") as! YourSecondViewController
//As someone's details are already saved so we auto-login and move to second view
}}
2) In your sign in button function , check whatever condition you want to check and then, inside the same, if condition satisfies then save data to userDefaults.
// If no details are saved in defaults, then control will come to this part, where we will save the entered userName and Password
let defaults = UserDefaults.standard
defaults.set(self.enteredUseName, forKey: "userName")
defaults.set(self.enteredPassword, forKey: "Password")
defaults.synchronize()
3) On logout button , delete the userDefaults and load the login view again :
let defaults = UserDefaults.standard
defaults.removeObject(forKey: "userName") //We Will delete the userDefaults
defaults.removeObject(forKey: "userPassword")
defaults.synchronize() //Sync. the defaults.
navigationController?.popToRootViewController(animated: true) //Move Back to initial view.
4) If you are using a navigation control, that you must be using :P then you will surely see the back button which will open the second view if clicked, for that you can hide the navigation bar in viewDidLoad() of your login view
self.navigationController?.navigationBar.isHidden = true