what I am trying to do is fetching data from firebase, but the data is nil because the user did not send his data to firebase yet, so when he enter the view controller that should show his data, the compiler make error. How can I solve this error? I tride to add alert, but it's still not working.
func getData(){
ref = Database.database().reference()
let userID = Auth.auth().currentUser?.uid
ref.child("users")
.queryOrdered(byChild: "uid")
.queryEqual(toValue:userID)
.observe(.value) { (snapshot, error) in
if error == nil{// alert} elses{
if let data = snapshot.value as? NSDictionary {
if snapshot.exists() {
for a in ((snapshot.value as AnyObject).allKeys)!{
let users = data.value(forKey:a as! String) as! NSDictionary
let address = users.value(forKey:"Address") as! NSDictionary
self.lblAddressNickname.text = address.value(forKey:"addressNickname") as? String
}
}
}
}
}
}
So as of now i understand the question that you have problem in fetching data from firebase when no data is in the firebase and then alert will come and it will redirect to a new controller?
So based on my understanding i will give answer if any problem of understanding things then reply me?
first you have to check that particular user have any data in firebase database so if there is no data then alert function will call
if let data == data
{
fetch_logic is here
}
else
{
let alert = UIAlertController(title:"Add Data",message:"",preferredStyle: .alert)
let action = UIAlertAction(title: "Add Button", style: .default) { (UIAlertAction) in
}
alert.addAction(action)
present(alert,animation:true,completion:true)
}
Related
Summary
I'm developing an application where users can reserve and cancel reservations for classes. In a ReservationButtonView I two buttons that add and remove a user to a workout class respectively. Currently the button I show is based off whether the user's Firebase Auth uid is listed in a Firestore document.
I was having issues when rapidly tapping on the reservation button. Specifically, the reservationCnt would become inaccurate by showing more or less than the actual users reserved for a class.
The only way I have found to resolve this is be using a Firestore transaction that checks to see if a user is in a workout class already. If they are, addReservation() now does nothing. If they aren't, removeReservation() would also do nothing.
At first I thought I could just disable the button and via the logic still in place the code below (.disabled()), but that alone didn't work as I ran into the above described race conditions. What I found out is that arrayUnion and arrayRemove still succeed even when the object I'm looking to add is there and not there respectively. Meaning it is possible for my transaction to not remove a reservedUser that isn't there and also decrease the reservationCnt which can leave me with say no reserved users and a reservationCnt of -1
The Ask
Is there a better way to handle this reservation process? Can I accomplish this without a transaction for at least the removal of users in some way. Ideally, I'd like to have a spinner replace the button as I add or remove a user's reservation to indicate to the user that the app is processing the request. Perhaps I need two variables to manage the disabled() state instead of one?
MVVM Code Snippets
NOTE: I pulled out some button styling to make the code a bit less verbose
ReservationButtonView
struct ReservationButtonView: View {
var workoutClass: WorkoutClass
#ObservedObject var viewModel: WorkoutClassViewModel
#EnvironmentObject var authViewModel: AuthViewModel
var body: some View {
if checkIsReserved(uid: authViewModel.user?.uid ?? "", reservedUsers: workoutClass.reservedUsers ?? []) {
Button(action: {
viewModel.isDisabled = true
viewModel.removeReservation(
documentId: workoutClass.id!,
reservedUserDetails: ["uid": authViewModel.user?.uid as Any, "photoURL": authViewModel.user?.photoURL?.absoluteString ?? "" as Any, "displayName": authViewModel.user?.displayName ?? "Bruin Fitness Member" as Any],
uid: authViewModel.user?.uid ?? "")
}){
Label(
title: { Text("Cancel Reservation")
.font(.title) },
icon: { Image(systemName: "person.badge.minus")
.font(.title) }
)
}.disabled(viewModel.isDisabled)
} else{
Button(action: {
viewModel.isDisabled = true
viewModel.addReservation(
documentId: workoutClass.id!,
reservedUserDetails: ["uid": authViewModel.user?.uid as Any, "photoURL": authViewModel.user?.photoURL?.absoluteString ?? "" as Any, "displayName": authViewModel.user?.displayName ?? "Bruin Fitness Member" as Any],
uid: authViewModel.user?.uid ?? "")
}){
Label(
title: { Text("Reserve")
.font(.title) },
icon: { Image(systemName: "person.badge.plus")
.font(.title) }
)
}
.disabled(viewModel.isDisabled)
}
}
}
func checkIsReserved(uid: String, reservedUsers: [reservedUser]) -> Bool {
return reservedUsers.contains { $0.uid == uid }
}
WorkoutClassModel
struct reservedUser: Codable, Identifiable {
var id: String = UUID().uuidString
var uid: String
var photoURL: URL?
var displayName: String?
enum CodingKeys: String, CodingKey {
case uid
case photoURL
case displayName
}
}
struct WorkoutClass: Codable,Identifiable {
#DocumentID var id: String?
var reservationCnt: Int
var time: String
var workoutType: String
var reservedUsers: [reservedUser]?
enum CodingKeys: String, CodingKey {
case id
case reservationCnt
case time
case workoutType
case reservedUsers
}
}
WorkoutClassViewModel
class WorkoutClassViewModel: ObservableObject {
#Published var isDisabled = false
private var db = Firestore.firestore()
func addReservation(documentId: String, reservedUserDetails: [String: Any], uid: String){
let incrementValue: Int64 = 1
let increment = FieldValue.increment(incrementValue)
let addUser = FieldValue.arrayUnion([reservedUserDetails])
let classReference = db.document("schedules/Redwood City/dates/\(self.stateDate.dbDateFormat)/classes/\(documentId)")
db.runTransaction { transaction, errorPointer in
let classDocument: DocumentSnapshot
do {
print("Getting classDocument for docId: \(documentId) in addReservedUser()")
try classDocument = transaction.getDocument(classReference)
} catch let fetchError as NSError {
errorPointer?.pointee = fetchError
return nil
}
guard let workoutClass = try? classDocument.data(as: WorkoutClass.self) else {
let error = NSError(
domain: "AppErrorDomain",
code: -3,
userInfo: [
NSLocalizedDescriptionKey: "Unable to retrieve workoutClass from snapshot \(classDocument)"
]
)
errorPointer?.pointee = error
return nil
}
let isReserved = self.checkIsReserved(uid: uid, reservedUsers: workoutClass.reservedUsers ?? [])
if isReserved {
print("user is already in class so therefore can't be added again")
return nil
} else {
transaction.updateData(["reservationCnt": increment, "reservedUsers": addUser], forDocument: classReference)
return nil
}
} completion: { object, error in
if let error = error {
print(error.localizedDescription)
self.isDisabled = false
} else {
print("Successfully ran transaction with object: \(object ?? "")")
self.isDisabled = false
}
}
}
func removeReservation(documentId: String, reservedUserDetails: [String: Any], uid: String){
let decrementValue: Int64 = -1
let decrement = FieldValue.increment(decrementValue)
let removeUser = FieldValue.arrayRemove([reservedUserDetails])
let classReference = db.document("schedules/Redwood City/dates/\(self.stateDate.dbDateFormat)/classes/\(documentId)")
db.runTransaction { transaction, errorPointer in
let classDocument: DocumentSnapshot
do {
print("Getting classDocument for docId: \(documentId) in addReservedUser()")
try classDocument = transaction.getDocument(classReference)
} catch let fetchError as NSError {
errorPointer?.pointee = fetchError
return nil
}
guard let workoutClass = try? classDocument.data(as: WorkoutClass.self) else {
let error = NSError(
domain: "AppErrorDomain",
code: -3,
userInfo: [
NSLocalizedDescriptionKey: "Unable to retrieve reservedUsers from snapshot \(classDocument)"
]
)
errorPointer?.pointee = error
return nil
}
let isReserved = self.checkIsReserved(uid: uid, reservedUsers: workoutClass.reservedUsers ?? [] )
if isReserved {
transaction.updateData(["reservationCnt": decrement, "reservedUsers": removeUser], forDocument: classReference)
return nil
} else {
print("user not in class so therefore can't be removed")
return nil
}
} completion: { object, error in
if let error = error {
print(error.localizedDescription)
self.isDisabled = false
} else {
print("Successfully ran removeReservation transaction with object: \(object ?? "")")
self.isDisabled = false
}
}
}
func checkIsReserved(uid: String, reservedUsers: [reservedUser]) -> Bool {
return reservedUsers.contains { $0.uid == uid }
}
}
App screenshot
Reservation button is the green/grey button at the bottom of the view
As this is a race condition, You have already acknowledged the use of Transactions for the update which is the most desirable as this can ensure the update is successful before allowing the App to change button status.
I.e. by using a transaction and only updating the UI Button state on success, which is explained here
The recommendation is to keep the state of the button mapped to what is in the document, therefore you are likely to exceed rate limits by updating the same field continuously based on the flipping of the button.
Another way to handle this tracking of the state of enrollment is to add a new document that indicates the state of the enrollment for the user to a collection that is the class they are enrolling in.
I.e. Rather than having the class user enrolling into being a document, make that a collection and each time the enrollment state changes, write a new document. This will allow for updates to occur without using transactions and the current state of enrollments is contained within the latest document. This latest document can be read and used as the status of the button within the App with the added benefit that the state will always update to the status contained within Firestore.
I ended up resolving this by adding a disable check conditional before the conditional that decides whether to show the "Reserve" or "Cancel" button.
This way when my Firestore transaction is running the user will see a spinner instead and can't monkey test the button. The spinner helps to show that the reservation operation is in progress. When the transaction hits its completion block I disable the isDisabled Bool and the listener is in sync (the user then sees the newly toggled button state)
if workoutClassVM.isDisabled {
ProgressView()
.progressViewStyle(CircularProgressViewStyle(tint: Color("bruinGreenColor")))
} else if checkIsReserved(uid: authVM.user?.uid ?? "", reservedUsers: workoutClass.reservedUsers ?? []) {
...
I have the fetch Data code here, but I don't understand how I am supposed to delete documents without setting the ID to the Document's ID. I was following this tutorial here. https://medium.com/swift-productions/swiftui-easy-to-do-list-with-firebase-2637c878cf1a I'm assuming I need to do so in the data mapping but I don't understand how with this code. I want to remove a todo from a SwiftUI list and also delete it's entire Firestore Document.
func fetchData() {
db.collection("todos").addSnapshotListener { (querySnapshot, error) in
guard let documents = querySnapshot?.documents else {
print("No documents")
return
}
self.todos = documents.map { (QueryDocumentSnapshot) -> Todo in
let data = QueryDocumentSnapshot.data()
let todoDetails = data["todo"] as? String ?? ""
return Todo(todoDetais: todoDetails)
}
}
}
View Model
struct Todo: Codable, Identifiable {
var id: String = UUID().uuidString
var todoDetais: String?
}
I recommend using Codable to map your Firestore documents to Swift structs. This will make your code easier to write, less prone to errors, and more type-safe.
Specifically, it will also enable you to use #DocumentID to map the Firestore document ID to the id attribute of your Swift struct.
Here's a quick example:
struct Book: Codable {
#DocumentID var id: String?
var title: String
var numberOfPages: Int
var author: String
}
func fetchBook(documentId: String) {
let docRef = db.collection("books").document(documentId)
docRef.getDocument { document, error in
if let error = error as NSError? {
self.errorMessage = "Error getting document: \(error.localizedDescription)"
}
else {
if let document = document {
do {
self.book = try document.data(as: Book.self)
}
catch {
print(error)
}
}
}
}
}
For more details, see this comprehensive guide I wrote about mapping Firestore documents to Swift structs (and back).
For more information about how to delete a Firestore document from a SwiftUI app, check out this article
Trying to query a document and then update it in a function in my ViewModel. Trying something like the below, but it doesn't work. Any advice would be appreciated!
func addToFruits(name: String) {
db.collection("fruits").whereField("name", isEqualTo: name)
.getDocument()
.limit(to: 1)
.updateData(["fruits": FieldValue.arrayUnion([name])])
}
func addToRoutine(routine: String, habit: String) {
db.collection("routines").whereField("name", isEqualTo: routine).getDocuments() { (querySnapshot, err) in
if let err = err {
print("Error getting documents: \(err)")
} else {
for document in querySnapshot!.documents {
document.updateData(["habits": FieldValue.arrayUnion([habit])])
}
}
}
}
In the first one, error I get is "Value of type 'Query' has no member 'getDocument'" and not sure how to resolve this. Second one, error I get is "Value of type 'QueryDocumentSnapshot' has no member 'updateData'"
It's not exactly clear what you're attempting to update but here's some quick example code that will read in a user named 'Steve' and update his age to 50. Keep in mind this will read in the FIRST user named 'Steve' and update their age - then when it's run again, will read the NEXT Steve etc etc - that may be what your attempting to do.
func readUsersAndUpdateTheirAgeTo50() {
let users = self.db.collection("users") //self.db points to *my* firestore
users.whereField("name", isEqualTo: "Steve").limit(to: 1).getDocuments(completion: { querySnapshot, error in
if let err = error {
print(err.localizedDescription)
return
}
guard let docs = querySnapshot?.documents else { return }
for doc in docs {
let docId = doc.documentID
let name = doc.get("name")
print(docId, name)
let ref = doc.reference
ref.updateData(["age": 20])
}
})
}
If I just wanted to update all Steve's age to 50, remove the limit
.limit(to: 1)
Note this code is kind of sloppy as since there is a limit of 1, we wouldn't need the loop. Also note that not every Steve is 50 so there should be additional parameters to narrow down which Steve it is - like a uid for example.
Below is the code for my signup page. I want to make it so that when someone creates an account on the sign up page, I create a document in the users collection and include uuid in the document. However, session.session?.uid ends up being nil. Does anyone know why this is?
struct SignUpView: View {
#State var email = ""
#State var password = ""
#State var name = ""
#State var error = ""
#EnvironmentObject var session: SessionStore
func signUp() {
let db = Firestore.firestore()
let user = db.collection("users").document()
let test = db.collection("users").document(user.documentID).collection("routines").document()
session.signUp(email: email, password: password) { (result, error) in
if let error = error {
self.error = error.localizedDescription
print("This is the error \(error)")
return
} else {
self.email = ""
self.password = ""
}
}
user.setData(["id": user.documentID, "email": email]) { (err) in
if err != nil {
print((err?.localizedDescription)!)
return
}
}
print(session.session?.uid)
test.setData(["id:": test.documentID, "msg": "samwell Tarly", "uuid": session.session?.uid]) { (err) in
print("ummmmm test data?")
if err != nil {
print((err?.localizedDescription)!)
return
}
}
}
The Firebase APIs are asynchronous, simply because they access a remote system, across the internet, which takes a little time. The same applies for accessing the local disk, by the way. This blog post explains this in more detail.
Consequently, session.signUp is an asynchronous process. I.e. the call to print(session.session?.uid) is executed before session.signUp returns. Thus, session.session?.uid is still nil.
To work around this, you can nest your calls like this:
session.signUp(email: email, password: password) { (result, error) in
if let error = error {
self.error = error.localizedDescription
print("This is the error \(error)")
return
}
else {
self.email = ""
self.password = ""
user.setData(["id": user.documentID, "email": email]) { (err) in
if err != nil {
print((err?.localizedDescription)!)
return
}
}
}
}
Generally speaking, I would strongly recommend to not perform so much logic in your views, but instead keep your views as anaemic as possible - meaning: put all your logic into view models, and bind the view to the view models by using Combine. This will make your code much cleaner, easier to test, and maintainable.
See https://peterfriese.dev/replicating-reminder-swiftui-firebase-part2/ for how to do this.
I am still having difficulty in checking whether the user is logged in with Google or Facebook to read and write on Firebase Database. I want to present a log in screen to a first time user and when the user authenticates, the log in screen is dismissed and it sent to the tabViewControllers. Here's my Swift 4 code below, which is placed in the AppDelegate, application(application:didFInishLaunchingWithOptions launchOptions:).
if Auth.auth().currentUser == nil {
print("NO USER") // this does print out in the console before the app crashes
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let loginVC = storyboard.instantiateViewController(withIdentifier: "loginVC") as! LogInViewController
self.window?.rootViewController = loginVC
} else {
let tabController = window!.rootViewController as! UITabBarController
if let tabViewControllers = tabController.viewControllers {
// First tab (only one so far...)
let navController = tabViewControllers[0] as! UINavigationController
let controller1 = navController.viewControllers.first as! UserProfileViewController
controller1.coreDataStack = coreDataStack
}
}
}
Please note the LogInViewController Scene is created in the Main.storyboard file and it has a Storyboard ID of "loginVC". When I try to run this, the program crashes at the part where the tabViewController[0] tries to fetch from the coreDataStack.
Hi you need to store UID of the user here is my code for login screen as you said if user open app for first time he have to login / authenticate and second time is automatically.
override func viewDidLoad() {
super.viewDidLoad()
if let uid = KeychainWrapper.standard.string(forKey: KEY_UID) {
autoLoginWithUID(uid: uid)
}
}
after app launches try it to auto login him if have stored his UID otherwise screen stays
func autoLoginWithUID(uid: String) {
KeychainWrapper.standard.set(uid, forKey: KEY_UID)
print(uid)
//Keep db and userRef as class constants shouldn't be here
let db = Firestore.firestore()
let userRef = db.collection("Users").document(uid)
userRef.getDocument { (document, error) in
if let document = document {
print("User data: \(document.data())")
self.performSegue(withIdentifier: "LogIn", sender: nil)
} else {
print("User does not exist")
}
}
}
Here I look in db if I have user with this UID if I got it its stored in global variable and continue. You can also store users credentials and log user by them. But dont know which way is more secure.
Auth.auth().signIn(with: credential) { (user, error) in
if let error = error {
// ...
return
}
// User is signed in
// ...
}
}
If you want more code from UserRequest let me know ;)