SwiftUI #Published variable not updating - firebase

Question

I have a class with a #Published variable named userData. When the function fbLogic.getUserData() is called in this class, it updates the userData array with the data which is populated from a call to Firestore database.
The issue is that this published variable is not updating in view which access it. Or more so, these functions don't wait until the Firestore call is finished before accessing the variable. So the BarGraphView() is called with empty reports[] array, and this array isn't updated by the convertToReports() call because convertToReports() is called with an empty userData array, because fbLogic.getUserData() hasn't finished retrieving the Firebase data yet. Hopefully the code explains it better.
This is the View which is making reference to the array.
struct StatsView: View {
let ID: String;
#EnvironmentObject var statsController: StatsDataController
#State var reports: [Report] = [Report]();
#Binding var fbLogic: FirebaseLogic
var body: some View {
BarGraphView(selection: $selection, reports: $reports, originalReports: $originalReports).environmentObject(statsController).onAppear{
fbLogic.userData = fbLogic.getUserData(uid: ID); //supposed to update the userData #Published var
//These are called before fbLogic.userData has even been updated !!!
self.reports = statsController.convertToReports(users: fbLogic.userData);
print("fblogic data ", fbLogic.userData, " ", ID);};
}
This View prints out "fb logic data []", before the call to .getUserData() has even finished, and so the call to convertToReports() happens with an empty array, instead of a populated array.
Please, how do I make this view recognise that the fbLogic.userData #Pubished array has updated and call convertToReports(), and redraw the BarGraphView with the POPULATED array.
Here is part of the fbLogic class so you can understand the call to firebase:
class FirebaseLogic: ObservableObject {
#Published var userData = [UserData]()
func getUserData(uid: String) -> [UserData]{
let db = Firestore.firestore()
userData = [UserData]()
let auth = Auth.auth();
let currentUser = (auth.currentUser?.uid)!
let data = db.collection("UserData").document(currentUser).collection("Data") .getDocuments { [self] (snapshot, error) in
guard let snapshot = snapshot, error == nil else {
return
}
print("Number of documents fb logic get user data: \(snapshot.documents.count ?? -1)")
snapshot.documents.forEach({ (documentSnapshot) in
let documentData = documentSnapshot.data()
//CONVERT TO userObject here (removed for simplicity)
userData.append(userObject)
})
}
return userData
}

Answer 1

Try using
#ObservedObject var fbLogic: FirebaseLogic
in StatsView. Make sure you pass an #ObservedObject type to StatsView when you pass data to this view from parent view.

Answer 2

The reason this isn't working is that the call to getDocuments() is asynchronous. So when you return the array of mapped documents (consider using Codable), it is still empty.
Here is an updated version of your code that assigns the mapped documents to the published property.
class FirebaseLogic: ObservableObject {
#Published var userData = [UserData]()
func getUserData(uid: String) -> [UserData] {
let db = Firestore.firestore()
let localUserData = [UserData]()
let auth = Auth.auth();
let currentUser = (auth.currentUser?.uid)! // (1)
db.collection("UserData").document(currentUser).collection("Data").getDocuments { [self] (snapshot, error) in
guard let snapshot = snapshot, error == nil else {
return
}
print("Number of documents fb logic get user data: \(snapshot.documents.count ?? -1)")
snapshot.documents.forEach { documentSnapshot in
let documentData = documentSnapshot.data()
// CONVERT TO userObject here (removed for simplicity)
localUserData.append(userObject)
}
self.userData = localUserData
}
}
}
You can further improve this code by using .map() to transform your documents. See this code snippet that is part of my article about mapping Firestore documents to/from Swift:
listenerRegistration = db.collection("programming-languages")
.addSnapshotListener { [weak self] (querySnapshot, error) in
guard let documents = querySnapshot?.documents else {
self?.errorMessage = "No documents in 'programming-languages' collection"
return
}
self?.programmingLanguages = documents.compactMap { queryDocumentSnapshot in
let result = Result { try queryDocumentSnapshot.data(as: ProgrammingLanguage.self) }
...