How do I store user data once logged in to be used throughout the app?

Question

When the user logs in, I am retrieving their data from Firebase and storing it in a struct in my LogInViewController. So to retrieve it from any ViewController, I just simply have to call LogInViewController.myVariables.person?.getFirstName() to get their first name and etc. But doesn't this create a memory usage issue because I am instantiating LogInViewController every time I call it? What is the best practice for storing user data to be used throughout all the ViewControllers? This is what a function in my SceneDelegate looks like.

 func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        if let windowScene = scene as? UIWindowScene {
                  let window = UIWindow(windowScene: windowScene)
                  let storyboard = UIStoryboard(name: "Main", bundle: nil)
                  if KeychainWrapper.standard.string(forKey: "email") != nil && KeychainWrapper.standard.string(forKey: "password") != nil { //if the keychain isn't nil, then sign-in
                    print("here keychainwrapper is not nil")
                       Auth.auth().signIn(withEmail: KeychainWrapper.standard.string(forKey: "email")!, password:  KeychainWrapper.standard.string(forKey: "password")!) { (result, error) in
                              if error == nil {
                                   if Auth.auth().currentUser!.isEmailVerified {
                                    self.getData(result!, completionHandler: { () in
                                        //gets data, then goes to TabBarController
                                        window.setRootViewController(storyboard.instantiateViewController(withIdentifier: "TabBarController"), options: UIWindow.TransitionOptions(direction: .fade))
                                        self.window = window
                                        window.makeKeyAndVisible()
                                      })
                                   }else{ //if they aren't verified
                                    window.setRootViewController(storyboard.instantiateViewController(withIdentifier: "ViewController"), options: UIWindow.TransitionOptions(direction: .fade))
                                    self.window = window
                                    window.makeKeyAndVisible()
                                }
                          }else{ //if there is a sign-in error                                window.setRootViewController(storyboard.instantiateViewController(withIdentifier: "ViewController"), options: UIWindow.TransitionOptions(direction: .fade))
                                self.window = window
                                window.makeKeyAndVisible()
                          }
                    }
    
                  }else{ //if keychain is nil
                    window.setRootViewController(storyboard.instantiateViewController(withIdentifier: "ViewController"), options: UIWindow.TransitionOptions(direction: .fade))
                    self.window = window
                    window.makeKeyAndVisible()
            }
        
       //guard let _ = (scene as? UIWindowScene) else { return }
        }
    }

func getData(_ result:AuthDataResult, completionHandler: @escaping() -> Void){
        let user = result.user
         let docRef = db.collection("Users").document(user.uid)
           docRef.getDocument {  (document, error) in
                     if document != nil && document!.exists {
                       let d = document!.data() 
                        LogInViewController.myVariables.person = Person(d!["firstName"]! as! String, d!["lastName"]! as! String)
                        completionHandler()
                }
        }
        
    }

Need some code, my friend. Also, can you clarify what you mean by "store". Are you persisting it on the device or just keeping it around when you're logged in. — Adrian, Aug 23 '20 at 17:25

score 1 · Accepted Answer · answered Aug 23 '20 at 17:54

1

You can use UserDefaults to store data for use across the app. How can I use UserDefaults in Swift?

Keep in mind it is not recommended for large chunks of data as the data gets loaded into memory everytime the app loads, for large data you're better off using some local database like Realm, Core Data etc.

answered Aug 23 '20 at 17:54

Vibhor

70
9

How much data is "large data"? – Kunal M Aug 23 '20 at 18:09
It is generally fine to store user properties and application preferences in UserDefaults but it is not a good place to store data which could grow with app usage. – Vibhor Aug 23 '20 at 18:15
Large data, say over a few MBs in UserDefaults could affect your initial app launch time. – Vibhor Aug 23 '20 at 18:17
I am only storing 600 bytes. – Kunal M Aug 23 '20 at 18:42

How do I store user data once logged in to be used throughout the app?

1 Answers1