How to call data from firebase synchronously - arrays

Question

I have a function that calls data from my Firebase Database, but it is an async function, and messing up the other functions of my app. I have looked all around tutorials but they only show asyncronus functions, and my app depends on the Firebase Data to load first.
Code for the function:
#State var realLat: [String] = [ ]
#State var realLong: [String] = [ ]
func downloadFirebaseData() async throws -> Float {
let group = DispatchGroup()
group.enter() // << start
let db = Firestore.firestore()
try withUnsafeThrowingContinuation { continuation in
db.collection("annotations")
.getDocuments { (querySnapshot, error) in
defer {
group.leave() // << end on any return
}
// result heading code here
if let Lat = i.document.get("lat") as? String {
DispatchQueue.main.async {
realLat.append(Lat)
print("downloadLatServerData() \(realLat)")
}
}
}
}
group.wait() // << block till leave
}
The function DownloadFirebaseMapServerData() is an async function becuase of the line db.collection("annotations").addSnapshotListener {(snap, err) in... and I need realLat and realLong to be downloaded first inorder to assign them to a mapAnnotation, so is there any way that I could make this function syncronus or make another function with the same end goal? Also another thing to note is that realLat and realLong are both String Arrays, or Arrays that are Strings

Answer 1

Ok, let's say that - try to avoid making synchronous API that designed asynchronous - it was done by purpose, long time-consuming bla-bla-bla
but, if it is needed technically it is possible, for example using dispatch groups, like
func downloadFirebaseData() async throws -> Float {
let group = DispatchGroup()
group.enter() // << start
let db = Firestore.firestore()
try withUnsafeThrowingContinuation { continuation in
db.collection("annotations")
.getDocuments { (querySnapshot, error) in
defer {
group.leave() // << end on any return
}
// result heading code here
}
}
group.wait() // << block till leave
}